- Email: [email protected]
The relationship between nucleated red blood cell counts and early-onset neonatal seizures
The relationship between nucleated red blood cell counts and early-onset neonatal seizures Sean C. Blackwell, MD, Jerrie S. Refuerzo, MD, Honor M. Wolfe, MD, Sonia S. Hassan, MD, Stanley M. Berry, MD, Robert J. Sokol, MD, and Yoram Sorokin, MD Detroit, Michigan OBJECTIVE: This study was undertaken to better define the timing of neurologic insult in neonates with early-onset seizures through evaluation of neonatal nucleated red blood cell levels. STUDY DESIGN: Medical records and the International Classification of Diseases, Ninth Revision codes were used to identify all term neonates with neonatal convulsions who were delivered at our institution (January 1, 1990–December 31, 1995). Each neonate with early-onset seizures was matched to the next 3 neonates who met the following criteria: gestational age ≥37 weeks, no early-onset seizures, birth weight ≥2800 g, umbilical artery pH ≥7.25, and a 5-minute Apgar score >7. Demographic characteristics, clinical factors, and mean initial nucleated red blood cell counts were compared between groups. RESULTS: During the 6-year study period, there were a total of 36,490 singleton term deliveries of infants who were alive at birth. Forty-five (0.1%) of these neonates had early-onset seizures. Thirty neonates with early-onset seizures met the inclusion criteria. Mean nucleated red blood cell counts (number of nucleated red blood cells per 100 white blood cells) for neonates with early-onset seizures were significantly increased compared with those of control neonates (18.4 ± 22.0 vs 4.6 ± 4.5; P < .0008). CONCLUSIONS: Our findings are suggestive of the hypothesis that neurologic injury leading to early-onset seizures often occurs before the intrapartum period. (Am J Obstet Gynecol 2000;182:1452-7.)
Key words: Nucleated red blood cell count, neonatal seizures, intrapartum asphyxia
Fetuses with hypoxia-induced neurologic injuries before labor have decreased tolerance to the stress of labor.1 Impaired reserve manifested as fetal distress may be interpreted as the offending insult rather than the effect of prior injury.2 In spite of convincing evidence that hypoxic-ischemic cerebral injury happens before labor in many cases,3-9 “bad baby” malpractice claims often allege that the occurrence of early-onset seizures and its resultant morbidity are a consequence of intrapartum asphyxia and suboptimal obstetric care.10-12 The fact that expert witnesses and plaintiffs’ attorneys have effectively argued that early-onset seizures are the result of preventable intrapartum events underscores the importance of better defining the timing of hypoxic-ischemic injury. Nucleated red blood cells increase in response to hypoxia-induced erythropoietin production.13 Although the exact time course from fetal hypoxia to increased nuFrom the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hutzel Hospital/Wayne State University. Certificate of Merit Award Paper, presented at the Sixty-seventh Annual Meeting of The Central Association of Obstetricians and Gynecologists, Maui, Hawaii, October 24-27, 1999. Reprint requests: Sean C. Blackwell MD, Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hutzel Hospital, 4707 St Antoine Blvd, Detroit, MI 48201. E-mail [email protected]. Copyright © 2000 by Mosby, Inc 0002-9378/2000 $12.00 + 0 6/6/106854 doi:10.1067/mob.2000.106854
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cleated red blood cell counts is unknown, on the basis of animal studies, an interval from 48 to 72 hours may be postulated. Studies in fetal sheep have demonstrated that, from the initial onset of a hypoxic exposure prompting the stimulation of erythropoietin in the fetal liver, at least 48 hours is required to be able to detect increased nucleated red blood cell production in the bone marrow.14-16 It is this physiologic time lag that has prompted interest in use of nucleated red blood cell counts in the peripheral blood to aid in the timing of hypoxia-induced fetal injury. The purpose of our study was to investigate whether neonates with early-onset seizures have increased nucleated red blood cell counts, suggesting an asphyxial injury before intrapartum events. Material and methods Term (≥37 weeks) neonates with early-onset seizures who were delivered at Hutzel Hospital between January 1, 1990, and December 31, 1995, were identified from medical records by use of the term convulsions in newborns (International Classification of Diseases, Ninth Revision, code 779.0). An early-onset seizure was defined as a seizure diagnosed by electroencephalography occurring within the first 72 hours of life. Maternal and neonatal charts were reviewed for confirmation of the diagnosis, pertinent demographic and clinical data, and determination of neonatal nucleated red blood cell count within the first
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Table I. Patient demographic and clinical data Variable
Early-onset seizures group (n = 30)
Control group (n = 90)
Statistical significance
25.0 ± 7.4 26 (86.7%) 39.3 ± 1.7 3201.5 ± 369.4 12 (40%) 14 (46.6%) 7.15 ± 0.22
24.8 ± 8.0 68 (76%) 39.5 ± 1.8 3322.0 ± 200.6 10 (11.1%) 12 (13.3%) 7.31 ± 0.06
NS NS NS NS P < .01 P < .01 P < .01
Maternal age (y) Black race Gestational age (wk) Birth weight (g) Meconium staining Cesarean delivery Umbilical artery pH NS, Not significant.
Table II. Comparison of neonates with early-onset seizures with and without an elevated nucleated red blood cell count Variable Clinical chorioamnionitis Meconium staining Umbilical artery pH Umbilical artery pH ≤7.00 Cesarean delivery for fetal indications
Normal nucleated red blood cell count (n = 15)
Elevated nucleated red blood cell count (n = 15)
Statistical significance
1 (7%) 9 (60%) 7.09 ± 0.18 3 (20%) 2 (13%)
NS P < .05 NS NS NS
2 (13%) 3 (20%) 7.15 ± 0.24 2 (13%) 4 (27%)
NS, Not significant.
12 hours of life. Each neonate with early-onset seizures was compared with the next 3 term neonates without early-onset seizures who had measurement of nucleated red blood cell counts within the first 12 hours of life and met the following criteria: singleton infant, birth weight >2800 g, 5-minute Apgar score >7, and an umbilical artery pH ≥7.25. Early-onset seizures and control pregnancies complicated by maternal diabetes, birth weight <10th percentile for gestational age, fetal structural anomalies, and blood group incompatibility were excluded. Neonatal nucleated red blood cell counts were determined by use of a blood smear with a Wright stain and expressed as the number of nucleated red blood cells per 100 white blood cells. A nucleated red blood cell count >10 per 100 white blood cells was considered elevated.17, 18 Power analysis to determine adequate study sample size (power of 0.8 and α < .05) indicated that 90 control neonates were necessary to detect a 25% difference between groups. Baseline nucleated red blood cell counts for the control population was taken from established values in the literature.18 Statistical analysis included the Student t test and χ2 where appropriate. P < .05 was considered significant. Results A total of 36,490 term, singleton, live-born neonates were delivered at Hutzel Hospital during the 6-year study period. Forty-five (0.1%) had early-onset seizures; 30 of these neonates with early-onset seizures met the study criteria and had measurement of nucleated red blood cell counts within the first 12 hours of life. These neonates were matched to 90 control neonates. There were no differences in maternal characteristics, gestational age, or
birth weight between the 2 groups (Table I). However, meconium-stained amniotic fluid and delivery by cesarean were more common in the early-onset seizures group. Mean umbilical cord pH was significantly lower in the early-onset seizures group. Five patients with early-onset seizures had umbilical pH ≤7.0, and 13 (43.3%) had a 5-minute Apgar score <7. Mean nucleated red blood cell counts for neonates with earlyonset seizures were significantly increased compared with those of control neonates (18.4 ± 22.0 vs 4.6 ± 4.5; P < .0008) (Fig 1). There were no differences in mean umbilical cord pH values, cases of umbilical cord pH ≤7.0, cesarean delivery rates for fetal indications, and clinical chorioamnionitis between neonates with early-onset seizures with or without an elevated nucleated red blood cell count (Table II). Neonates with early-onset seizures and elevated nucleated red blood cell counts were more likely to have meconium-stained amniotic fluid (P < .05). Comment The finding of elevated nucleated red blood cell counts among neonates with early-onset seizures compared with gestational age–matched control neonates are suggestive of the theory that early-onset seizures often result from hypoxic-ischemic injury before the onset of labor. This suggests that the timing of the hypoxicischemic insult occurred from 48 hours to 7 days before delivery.13-16 However, 50% of the early-onset seizure cases were associated with normal nucleated red blood cell counts. We speculate that the neurologic injury either occurred at least 7 days before delivery, after which
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Fig 1. Distribution of nucleated red blood cell count per 100 white blood cells (NRBC/100WBC) from neonates with development of early-onset seizures compared with control neonates.
time the nucleated red blood cell counts would have returned to normal levels, or proximate to delivery, which would not have given enough time for the stimulation of erythropoietin to increase fetal nucleated red blood cell counts. The possibility also remains that the etiologic insult may be related not to asphyxia but to another mechanism such as a maternal or intrauterine infectious process.19 We chose early-onset seizure as our primary outcome because of its specificity as a marker for encephalopathy, its high predictability for long-term neurologic morbidity, and its often-alleged association with intrapartum asphyxia and suboptimal obstetric care.11, 12, 20, 21 Our findings are consistent with the prior studies of Phelan et al18, 22 and Korst et al,23 who found nucleated red blood cell levels to be significantly increased in neurologically impaired neonates compared with control neonates. They classified the timing of neurologic injury on the basis of fetal heart rate patterns and the process of the following clinical events: injury before labor, injury during the intrapartum period that lasted for some duration, or an acute intrapartum injury. Although all groups had increased nucleated red blood cell counts compared with control neonates, neonates with preadmission injury patterns had the highest counts. Mean nucleated red blood cell counts were similar between their control neonates and ours, and there was not a statistically significant difference in nucleated red blood cell counts between their injured neonates compared with our neonates with early-onset seizures.18 There are two main limitations to our study. Although
it was based on well-conducted animal studies, the true relationship between the time course of an asphyxial insult and an increase in nucleated red blood cells in the human fetus remains speculative. In addition, the threshold of hypoxia-ischemia necessary to produce either an increased nucleated red blood cell count or fetal neurologic injury in the human fetus is unknown. Data from neuropathologic findings at autopsy,4, 7, 8 cerebral imaging studies,6 and fetal heart rate patterns3, 5, 9, 10 all support the contention that the timing of brain injury is often remote from labor. However, in many cases in which neonatal impairment developed, these studies are not available or are not performed. Even when fetal heart rate tracings are available, the lack of specificity and the subjective nature of their interpretation may preclude their reliability.24, 25 In spite of the current knowledge of the timing of fetal brain injury, it is difficult to prove in an individual case that the primary insult did not occur during the intrapartum period. In conclusion, the finding of an increased nucleated red blood cell count in a neonate with development of early-onset seizures suggests a hypoxicischemic insult before the intrapartum period. This finding may aid in the defense of claims that suggest that suboptimal intrapartum care was given and that intervention would have prevented neurologic injury. REFERENCES
1. Goodlin RC. Do concepts of causes and prevention of cerebral palsy require revision? Am J Obstet Gynecol 1996;172:1830-6.
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2. Perlman JM. Intrapartum hypoxic-ischemic cerebral injury and subsequent cerebral palsy: medicolegal issues. Pediatrics 1997;99:851-9. 3. Keegan KA, Waffarn F, Quilligan EJ. Obstetrical characteristics and fetal heart rate patterns of infants who convulse during the newborn period. Am J Obstet Gynecol 1985;153:732-7. 4. Sims ME, Turkel SB, Halterman PA, Paul RH. Brain injury and intrauterine death. Am J Obstet Gynecol 1985;151:721. 5. Paul R, Yonekura L, Cantrall CJ, Turkel S, Pavlova, Sipos L. Fetal injury prior to labor: does it happen? Am J Obstet Gynecol 1986;154:1187-93. 6. Ellis WG, Goetzman BW, Lindenberg JA. Neuropathologic documentation of prenatal brain injury. Am J Dis Child 1988; 142:858-66. 7. Low JA, Robertson DM, Simpson LL. Temporal relationships of neuropathologic conditions caused by perinatal asphyxia. Am J Obstet Gynecol 1989;160:608-14. 8. Phelan JP, Ahn MO. Perinatal observations in forty-eight neurologically impaired term infants. Am J Obstet Gynecol 1994;171:424-31. 9. Lein JM, Towers CV, Quilligan EJ, de Veciana M, Toohey JS, Morgan MA. Term early-onset seizures: obstetrical characteristics, etiologic classifications, and perinatal care. Obstet Gynecol 1995;85:163-9. 10. Dennis J. Neonatal convulsions: Aetiology late neonatal status and long term outcome. Dev Med Child Neurol 1978;20:143-53. 11. Dennis J, Chalmers I. Very early neonatal seizure rate: a possible epidemiological indicator of the quality of perinatal care. Br J Obstet Gynaecol 1982;89:418-26. 12. Minchom P, Niswander K, Chalmers I. Antecedents and outcome of very early neonatal seizures in infants born at or after term. Br J Obstet Gynaecol 1987;94:431-9. 13. Maier RF, Bohme K, Dudenhausen JW, Obladen M. Cord blood erythropoietin in relation to different markers of fetal hypoxia. Obstet Gynecol 1993;81:575-80. 14. Widnes JA, Teramo KA, Clemons GK, Garcia JF, Calvalieri RL, Piasecki GJ, et al. Temporal response of immunoreactive erythropoietin to acute hypoxemia in fetal sheep. Pediatr Res 1986;20:15-9. 15. Kitnaka T, Alonso JG, Gilbert RD, Siu BL, Clemons GK, Longo LD. Fetal response to long-term hypoxemia in sheep. Am J Physiol 1989;256:R1348-54. 16. Georgieff MK, Schmidt RL, Mills MM, Radmer WJ, Widness JA. Fetal iron and cytochrome c status after intrauterine hypoxemia and erythropoietin administration. Am J Physiol 1992;262:R485-91. 17. Javert CT. The occurrence and significance of nucleated erythrocytes in the fetal vessels of the placenta. Am J Obstet Gynecol 1939;37:184-94. 18. Phelan JP, Ahn MO, Korst LM, Martin GI. Nucleated red blood cells: a marker for fetal asphyxia? Am J Obstet Gynecol 1995;173:1380-4. 19. Grether JK. Nelson KB. Maternal infection and cerebral palsy in infants of normal birth weight. JAMA 1997;278:207-11. 20. Volpe J. Hypoxic-ischemic encephalopathy: clinical aspects. In: Volpe J, editor. Neurology of the newborn. 3rd ed. Philadelphia: WB Saunders; 1995. p. 314-69. 21. American College of Obstetricians and Gynecologists. Fetal and neonatal neurologic injury. Washington: The College; 1992 Jan. Technical Bulletin No.: 163. 22. Phelan JP, Korst LM, Ahn MO, Martin GI. Neonatal nucleated red blood cell and lymphocyte counts in fetal brain injury. Obstet Gynecol 1998;91:485-9. 23. Korst LM, Phelan JP, Ahn MO, Martin GI. Nucleated red blood cells: an update on the marker for fetal asphyxia Am J Obstet Gynecol 1996;175:843-6. 24. Rosen MG. Dickinson JC. The paradox of electronic fetal monitoring: more data may not enable us to predict or prevent infant neurologic morbidity. Am J Obstet Gynecol 1993;168:745-51. 25. Nelson KB, Dambrosia JM, Ting TY, Grether JK. Uncertain value of electronic fetal monitoring in predicting cerebral palsy. N Engl J Med 1996;334:613-8.
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Discussion DR JOHN GIANOPOULOS, Maywood, Illinois. The discipline of obstetrics in the current environment in the United States has been under siege by plaintiffs’ attorneys and the public at large criticizing obstetric care and assessing arguments of causality for poor neurologic outcomes in neonates attributed to care rendered at the time of delivery. There have been multiple litigations across the country that have resulted in significant financial awards being given to patients, with the resultant 30% fee to the plaintiffs’ attorneys, with obstetric care blamed for poor outcomes. We as a discipline have been partially responsible for this dilemma. The concepts of fetal heart rate monitoring and umbilical blood gas measurements have been used as ammunition to fight the battle against obstetricians in the provision of obstetric care, with claims of significant injury because of events at or around the time of a child’s birth without sufficient data to support these claims. It is now well known from cerebral palsy literature that most (90%) handicaps incurred in the newborn period are related to events that occur antenatally, before the onset of the intrapartum period, or in the immediate neonatal period. Approximately 10% of neonatal handicaps caused by asphyxial injury may be directly attributed to intrapartum events. We, as a discipline, are looking to find scientific, quantifiable data to defend ourselves against accusations of causality for neurologic handicaps resulting from care rendered at the time of labor. The concept of assessing components of neonatal blood to retrospectively assess timing of neonatal injury is not a new one. Naeye and Localio1 first reported in November of 1995 the concept of neonatal lymphocytes and red blood cell normoblasts (ie, nucleated red blood cells) as potential markers for timing of hypoxic insult. Korst et al2 and Phelan et al3, 4 have multiple citations in the literature, with nucleated red blood cells used as a potential marker for neonatal brain injury. In the presence of a hypoxic insult, fetal erythropoietin is released and stimulates the early release of red blood cells from the bone marrow to increase hematocrit and increase the oxygen-carrying capacity of the blood. Animal data suggest that nucleated red blood cells do not occur in the fetal circulation until 48 to 72 hours after a hypoxically stimulated event and remain for approximately 7 days. However, the time course for fetal hypoxia to increased nucleated red blood cell count in the human fetus is unknown. It has been postulated that an elevated level of nucleated red blood cells found in the neonatal period in the first 12 hours of life is correlated with hypoxic events 48 to 72 hours before the time of birth and that elevated nucleated red blood cells in the immediate newborn period may be used as a marker to signify that the events that led to the neonatal injury occurred before labor and may be used defensively in litigation to objectively and quantitatively time neonatal injury remote from the time of delivery. Phelan et al3 showed that the highest level of nucleated red blood cells was found in infants born with classical signs of asphyxia and that the level of nucleated red
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blood cells tended to correlate with the timing of fetal neurologic injury. Korst et al2 reported the follow-up of their continuing studies and concluded that increased nucleated red blood cells does identify the presence of fetal asphyxia, and distinct nucleated red blood cell patterns may be helpful in relating to the timing of injury. The authors have presented an interesting assessment of nucleated red blood cells as a potential marker for antepartum intrauterine fetal events that may lead to neurologic injury, producing early neonatal seizures. The authors chose early-onset neonatal seizures as a marker for fetal neurologic injury and asphyxial events. Early neonatal seizures have been implicated, with a high level of correlation with long-term cerebral palsy. The authors used a retrospective approach correlating elevated nucleated red blood cells in patients with early-onset neonatal seizures and matching them to control patients without neonatal seizures. Patients with intrauterine growth restriction, diabetes mellitus, and prematurity were excluded from the eligibility criteria because all three of these conditions have been associated with elevated levels of neonatal nucleated red blood cells. The authors found that those patients with early-onset neonatal seizures had a significantly increased level of nucleated red blood cells compared with neonates without early-onset seizures and concluded that their data may support the hypothesis that neurologic injury leading to early-onset seizures often occurs before the intrapartum period. I believe that the results are clearly presented and the conclusions are well founded, given the data presented. However, I do have some concerns with the data and conclusions drawn. First, the authors assume that nucleated red blood cells indicate the time of neurologic injury to be between 48 hours and 7 days before delivery. However, the data that associate the exact time course from fetal hypoxia to increased nucleated red blood cell count are unknown in human beings and are based on animal studies. Did you carefully review the animal data? How strongly can we associate animal data to our human experience? Of the 30 patients with early-onset neonatal seizures, there was a significantly lower umbilical artery pH, a mean of 7.15 in the early-onset seizure group versus a mean of 7.31 in the control group. When the data are analyzed for those patients with a normal nucleated red blood cell count versus those patients with an elevated nucleated red blood cell count in the early-onset seizure group, the level of umbilical artery pH <7.0 was not significant in either category. It would be interesting to know what the mean umbilical artery pH levels were in each of the 2 groups. If the umbilical artery pH was significantly depressed in the normal nucleated red blood cell group versus the elevated nucleated red blood cell group leading to earlyonset seizures, one may be able to postulate that those patients with a normal nucleated red blood cell count who had early-onset seizures did experience a significant acute asphyxial event leading to lower umbilical artery pH levels. Therefore was there a difference in the mean umbilical artery pH in the early-onset seizure group with
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a normal nucleated red blood cell count versus the earlyonset seizure group that had an elevated nucleated red blood cell count? The authors state that it is difficult to prove in an individual case that the primary insult did not occur during the intrapartum period. This may be true; however, I contend that, with our entire armamentarium of umbilical blood gas data, the absence or presence of nucleated red blood cells in neonatal blood, the absence or presence of lymphocytes in neonatal blood, and fetal heart rate monitor patterns in an objective, evidence-based manner with ethical expert witnesses reviewing both sides for plaintiff and physician, the dilemma of causality and assessing blame on intrapartum care may be reduced. I believe that the authors should be complemented on a very well done piece of work. It supports earlier findings and adds to our knowledge in the literature. My last recommendation to the authors is that they de-emphasize the strength of their findings. They conclude that the findings support the hypothesis that nucleated red blood cells may be used in timing neonatal injury. However, because it is not known from human data the exact timing of the injury and the timing is inferred from animal data, I believe a less strong statement, such as “our findings may be suggestive or are potentially supportive of this hypothesis,” may be more appropriate, because this work will likely serve as supportive literature in closing arguments in courtrooms around the United States. REFERENCES
1. Naeye RL, Localio AR. Timing hypoxemic brain damage. Obstet Gynecol 1995;86:718-9. 3. Phelan JP, Ahn, MO, Korst LM, Martin GI. Nucleated red blood cells: a marker for fetal asphyxia? Am J Obstet Gynecol 1995;173:1380-4. 2. Korst LM, Phelan JP, Ahn MO, Martin GI. Nucleated red blood cells: an update on the marker for asphyxia. Am J Obstet Gynecol 1996;175:843-6. 4. Phelan JP, Korst LM, Ahn MO, Martin GI. Neonatal nucleated red blood cell and lymphocyte counts in fetal brain injury. Obstet Gynecol 1998;91:485-9.
DR ROBERT CARPENTER, Houston, Texas. One other marker that has been used for true intrapartum asphyxia is creatine phosphokinase isoenzymes and BB fraction. Some units will routinely use that in such babies. Does your unit do that? Do you have any potential data that could be analyzed? UNIDENTIFIED SPEAKER. Were any data available in this review that examined the placentas that should also be evaluated and perhaps used to time the injury? DR PAT COLLINS, Maywood, Illinois. The early-onset seizure data and the cases were presented as both clinical and electroencephalographic data. Clinical diagnosis of seizures in a newborn is notoriously difficult. What proportion of data was clinically based versus obtained by means of electroencephalography? The data were presented as a ratio of nucleated red blood cells to the white blood cell count and as a standardization to the white blood cell count. Were the white blood cell counts in the control neonates and the cases similar?
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DR WILLIAM P. GIDEON, Norman, Oklahoma. On the electroencephalograms, was any analysis done for localization? Was any family history extracted for history of epilepsy, mental retardation, or degenerative neurologic disorders? Was any scanning performed that might have also shown anatomic defects as a cause of the seizure activity? DR BLACKWELL (Closing). Neurologic injury in term fetuses is unfortunately an area that we do not know nearly enough about. Why certain fetuses are able to tolerate certain events whereas others readily decompensate is beyond our current understanding. One of the inherent problems is that in many cases fetal injury is not recognized immediately. It may be 12 to 24 hours before profound neonatal symptoms develop, and, depending on who is attending the delivery (perinatologist, general obstetrician, family practitioner, or midwife) and where it occurs (tertiary care hospital, community hospital), tests such as umbilical cord blood analysis and placental pathologic study may not be routinely performed. Even in university-based tertiary care centers such as ours, these studies are at times absent in cases with adverse fetal outcomes. A second problem is that fetal injury at term is an infrequent, often predictable event. These two facts together make it quite difficult to conduct clinical studies. That is why we were essentially relegated to performing this type of retrospective study. So, even in the best of circumstances, for many patients we were unable to get a clear idea of the pathophysiologic condition involved. In the medicolegal arena clinicians are often left with-
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out an umbilical pH level for exclusion of intrapartum acidemia or placental evidence of chronic prenatal disease, and experts, even outside of the courtroom, will disagree about the clinical significance of various fetal heart rate patterns. This is why the neonatal nucleated red blood cell count, as a measure for the timing of the onset of in utero hypoxic ischemia, is an attractive diagnostic tool. The entry criterion for the study was the presence of seizures by either clinical or electroencephalographic means. In fact, all neonates had both. The clinical diagnosis of seizure was taken from notations in the neonatal medical record by the neonatologist, pediatrician, or nurse practitioner. We did not analyze various aspects of the electroencephalogram. Patients were excluded if there was a maternal history of a seizure disorder; however, the presence or absence of a family history of epilepsy was not described in the charts. We also excluded patients if there was a structural fetal defect detected by prenatal ultrasonography. In this analysis we did not include placental examination, although we are currently in the process of this work. Even in the best of circumstances, if one is able to put together the fetal heart rate pattern, umbilical cord pH at delivery, neonatal nucleated red blood cell count, and neuroimaging studies of injured neonates, I am not exactly certain whether it will be possible to come up with a clear explanation or obvious pattern of causation. The final episode of brain injury may be a result of a combination or synergy of various factors, with each fetus having a different threshold.
Key words: Nucleated red blood cell count, neonatal seizures, intrapartum asphyxia
Fetuses with hypoxia-induced neurologic injuries before labor have decreased tolerance to the stress of labor.1 Impaired reserve manifested as fetal distress may be interpreted as the offending insult rather than the effect of prior injury.2 In spite of convincing evidence that hypoxic-ischemic cerebral injury happens before labor in many cases,3-9 “bad baby” malpractice claims often allege that the occurrence of early-onset seizures and its resultant morbidity are a consequence of intrapartum asphyxia and suboptimal obstetric care.10-12 The fact that expert witnesses and plaintiffs’ attorneys have effectively argued that early-onset seizures are the result of preventable intrapartum events underscores the importance of better defining the timing of hypoxic-ischemic injury. Nucleated red blood cells increase in response to hypoxia-induced erythropoietin production.13 Although the exact time course from fetal hypoxia to increased nuFrom the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hutzel Hospital/Wayne State University. Certificate of Merit Award Paper, presented at the Sixty-seventh Annual Meeting of The Central Association of Obstetricians and Gynecologists, Maui, Hawaii, October 24-27, 1999. Reprint requests: Sean C. Blackwell MD, Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hutzel Hospital, 4707 St Antoine Blvd, Detroit, MI 48201. E-mail [email protected]. Copyright © 2000 by Mosby, Inc 0002-9378/2000 $12.00 + 0 6/6/106854 doi:10.1067/mob.2000.106854
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cleated red blood cell counts is unknown, on the basis of animal studies, an interval from 48 to 72 hours may be postulated. Studies in fetal sheep have demonstrated that, from the initial onset of a hypoxic exposure prompting the stimulation of erythropoietin in the fetal liver, at least 48 hours is required to be able to detect increased nucleated red blood cell production in the bone marrow.14-16 It is this physiologic time lag that has prompted interest in use of nucleated red blood cell counts in the peripheral blood to aid in the timing of hypoxia-induced fetal injury. The purpose of our study was to investigate whether neonates with early-onset seizures have increased nucleated red blood cell counts, suggesting an asphyxial injury before intrapartum events. Material and methods Term (≥37 weeks) neonates with early-onset seizures who were delivered at Hutzel Hospital between January 1, 1990, and December 31, 1995, were identified from medical records by use of the term convulsions in newborns (International Classification of Diseases, Ninth Revision, code 779.0). An early-onset seizure was defined as a seizure diagnosed by electroencephalography occurring within the first 72 hours of life. Maternal and neonatal charts were reviewed for confirmation of the diagnosis, pertinent demographic and clinical data, and determination of neonatal nucleated red blood cell count within the first
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Table I. Patient demographic and clinical data Variable
Early-onset seizures group (n = 30)
Control group (n = 90)
Statistical significance
25.0 ± 7.4 26 (86.7%) 39.3 ± 1.7 3201.5 ± 369.4 12 (40%) 14 (46.6%) 7.15 ± 0.22
24.8 ± 8.0 68 (76%) 39.5 ± 1.8 3322.0 ± 200.6 10 (11.1%) 12 (13.3%) 7.31 ± 0.06
NS NS NS NS P < .01 P < .01 P < .01
Maternal age (y) Black race Gestational age (wk) Birth weight (g) Meconium staining Cesarean delivery Umbilical artery pH NS, Not significant.
Table II. Comparison of neonates with early-onset seizures with and without an elevated nucleated red blood cell count Variable Clinical chorioamnionitis Meconium staining Umbilical artery pH Umbilical artery pH ≤7.00 Cesarean delivery for fetal indications
Normal nucleated red blood cell count (n = 15)
Elevated nucleated red blood cell count (n = 15)
Statistical significance
1 (7%) 9 (60%) 7.09 ± 0.18 3 (20%) 2 (13%)
NS P < .05 NS NS NS
2 (13%) 3 (20%) 7.15 ± 0.24 2 (13%) 4 (27%)
NS, Not significant.
12 hours of life. Each neonate with early-onset seizures was compared with the next 3 term neonates without early-onset seizures who had measurement of nucleated red blood cell counts within the first 12 hours of life and met the following criteria: singleton infant, birth weight >2800 g, 5-minute Apgar score >7, and an umbilical artery pH ≥7.25. Early-onset seizures and control pregnancies complicated by maternal diabetes, birth weight <10th percentile for gestational age, fetal structural anomalies, and blood group incompatibility were excluded. Neonatal nucleated red blood cell counts were determined by use of a blood smear with a Wright stain and expressed as the number of nucleated red blood cells per 100 white blood cells. A nucleated red blood cell count >10 per 100 white blood cells was considered elevated.17, 18 Power analysis to determine adequate study sample size (power of 0.8 and α < .05) indicated that 90 control neonates were necessary to detect a 25% difference between groups. Baseline nucleated red blood cell counts for the control population was taken from established values in the literature.18 Statistical analysis included the Student t test and χ2 where appropriate. P < .05 was considered significant. Results A total of 36,490 term, singleton, live-born neonates were delivered at Hutzel Hospital during the 6-year study period. Forty-five (0.1%) had early-onset seizures; 30 of these neonates with early-onset seizures met the study criteria and had measurement of nucleated red blood cell counts within the first 12 hours of life. These neonates were matched to 90 control neonates. There were no differences in maternal characteristics, gestational age, or
birth weight between the 2 groups (Table I). However, meconium-stained amniotic fluid and delivery by cesarean were more common in the early-onset seizures group. Mean umbilical cord pH was significantly lower in the early-onset seizures group. Five patients with early-onset seizures had umbilical pH ≤7.0, and 13 (43.3%) had a 5-minute Apgar score <7. Mean nucleated red blood cell counts for neonates with earlyonset seizures were significantly increased compared with those of control neonates (18.4 ± 22.0 vs 4.6 ± 4.5; P < .0008) (Fig 1). There were no differences in mean umbilical cord pH values, cases of umbilical cord pH ≤7.0, cesarean delivery rates for fetal indications, and clinical chorioamnionitis between neonates with early-onset seizures with or without an elevated nucleated red blood cell count (Table II). Neonates with early-onset seizures and elevated nucleated red blood cell counts were more likely to have meconium-stained amniotic fluid (P < .05). Comment The finding of elevated nucleated red blood cell counts among neonates with early-onset seizures compared with gestational age–matched control neonates are suggestive of the theory that early-onset seizures often result from hypoxic-ischemic injury before the onset of labor. This suggests that the timing of the hypoxicischemic insult occurred from 48 hours to 7 days before delivery.13-16 However, 50% of the early-onset seizure cases were associated with normal nucleated red blood cell counts. We speculate that the neurologic injury either occurred at least 7 days before delivery, after which
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Fig 1. Distribution of nucleated red blood cell count per 100 white blood cells (NRBC/100WBC) from neonates with development of early-onset seizures compared with control neonates.
time the nucleated red blood cell counts would have returned to normal levels, or proximate to delivery, which would not have given enough time for the stimulation of erythropoietin to increase fetal nucleated red blood cell counts. The possibility also remains that the etiologic insult may be related not to asphyxia but to another mechanism such as a maternal or intrauterine infectious process.19 We chose early-onset seizure as our primary outcome because of its specificity as a marker for encephalopathy, its high predictability for long-term neurologic morbidity, and its often-alleged association with intrapartum asphyxia and suboptimal obstetric care.11, 12, 20, 21 Our findings are consistent with the prior studies of Phelan et al18, 22 and Korst et al,23 who found nucleated red blood cell levels to be significantly increased in neurologically impaired neonates compared with control neonates. They classified the timing of neurologic injury on the basis of fetal heart rate patterns and the process of the following clinical events: injury before labor, injury during the intrapartum period that lasted for some duration, or an acute intrapartum injury. Although all groups had increased nucleated red blood cell counts compared with control neonates, neonates with preadmission injury patterns had the highest counts. Mean nucleated red blood cell counts were similar between their control neonates and ours, and there was not a statistically significant difference in nucleated red blood cell counts between their injured neonates compared with our neonates with early-onset seizures.18 There are two main limitations to our study. Although
it was based on well-conducted animal studies, the true relationship between the time course of an asphyxial insult and an increase in nucleated red blood cells in the human fetus remains speculative. In addition, the threshold of hypoxia-ischemia necessary to produce either an increased nucleated red blood cell count or fetal neurologic injury in the human fetus is unknown. Data from neuropathologic findings at autopsy,4, 7, 8 cerebral imaging studies,6 and fetal heart rate patterns3, 5, 9, 10 all support the contention that the timing of brain injury is often remote from labor. However, in many cases in which neonatal impairment developed, these studies are not available or are not performed. Even when fetal heart rate tracings are available, the lack of specificity and the subjective nature of their interpretation may preclude their reliability.24, 25 In spite of the current knowledge of the timing of fetal brain injury, it is difficult to prove in an individual case that the primary insult did not occur during the intrapartum period. In conclusion, the finding of an increased nucleated red blood cell count in a neonate with development of early-onset seizures suggests a hypoxicischemic insult before the intrapartum period. This finding may aid in the defense of claims that suggest that suboptimal intrapartum care was given and that intervention would have prevented neurologic injury. REFERENCES
1. Goodlin RC. Do concepts of causes and prevention of cerebral palsy require revision? Am J Obstet Gynecol 1996;172:1830-6.
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2. Perlman JM. Intrapartum hypoxic-ischemic cerebral injury and subsequent cerebral palsy: medicolegal issues. Pediatrics 1997;99:851-9. 3. Keegan KA, Waffarn F, Quilligan EJ. Obstetrical characteristics and fetal heart rate patterns of infants who convulse during the newborn period. Am J Obstet Gynecol 1985;153:732-7. 4. Sims ME, Turkel SB, Halterman PA, Paul RH. Brain injury and intrauterine death. Am J Obstet Gynecol 1985;151:721. 5. Paul R, Yonekura L, Cantrall CJ, Turkel S, Pavlova, Sipos L. Fetal injury prior to labor: does it happen? Am J Obstet Gynecol 1986;154:1187-93. 6. Ellis WG, Goetzman BW, Lindenberg JA. Neuropathologic documentation of prenatal brain injury. Am J Dis Child 1988; 142:858-66. 7. Low JA, Robertson DM, Simpson LL. Temporal relationships of neuropathologic conditions caused by perinatal asphyxia. Am J Obstet Gynecol 1989;160:608-14. 8. Phelan JP, Ahn MO. Perinatal observations in forty-eight neurologically impaired term infants. Am J Obstet Gynecol 1994;171:424-31. 9. Lein JM, Towers CV, Quilligan EJ, de Veciana M, Toohey JS, Morgan MA. Term early-onset seizures: obstetrical characteristics, etiologic classifications, and perinatal care. Obstet Gynecol 1995;85:163-9. 10. Dennis J. Neonatal convulsions: Aetiology late neonatal status and long term outcome. Dev Med Child Neurol 1978;20:143-53. 11. Dennis J, Chalmers I. Very early neonatal seizure rate: a possible epidemiological indicator of the quality of perinatal care. Br J Obstet Gynaecol 1982;89:418-26. 12. Minchom P, Niswander K, Chalmers I. Antecedents and outcome of very early neonatal seizures in infants born at or after term. Br J Obstet Gynaecol 1987;94:431-9. 13. Maier RF, Bohme K, Dudenhausen JW, Obladen M. Cord blood erythropoietin in relation to different markers of fetal hypoxia. Obstet Gynecol 1993;81:575-80. 14. Widnes JA, Teramo KA, Clemons GK, Garcia JF, Calvalieri RL, Piasecki GJ, et al. Temporal response of immunoreactive erythropoietin to acute hypoxemia in fetal sheep. Pediatr Res 1986;20:15-9. 15. Kitnaka T, Alonso JG, Gilbert RD, Siu BL, Clemons GK, Longo LD. Fetal response to long-term hypoxemia in sheep. Am J Physiol 1989;256:R1348-54. 16. Georgieff MK, Schmidt RL, Mills MM, Radmer WJ, Widness JA. Fetal iron and cytochrome c status after intrauterine hypoxemia and erythropoietin administration. Am J Physiol 1992;262:R485-91. 17. Javert CT. The occurrence and significance of nucleated erythrocytes in the fetal vessels of the placenta. Am J Obstet Gynecol 1939;37:184-94. 18. Phelan JP, Ahn MO, Korst LM, Martin GI. Nucleated red blood cells: a marker for fetal asphyxia? Am J Obstet Gynecol 1995;173:1380-4. 19. Grether JK. Nelson KB. Maternal infection and cerebral palsy in infants of normal birth weight. JAMA 1997;278:207-11. 20. Volpe J. Hypoxic-ischemic encephalopathy: clinical aspects. In: Volpe J, editor. Neurology of the newborn. 3rd ed. Philadelphia: WB Saunders; 1995. p. 314-69. 21. American College of Obstetricians and Gynecologists. Fetal and neonatal neurologic injury. Washington: The College; 1992 Jan. Technical Bulletin No.: 163. 22. Phelan JP, Korst LM, Ahn MO, Martin GI. Neonatal nucleated red blood cell and lymphocyte counts in fetal brain injury. Obstet Gynecol 1998;91:485-9. 23. Korst LM, Phelan JP, Ahn MO, Martin GI. Nucleated red blood cells: an update on the marker for fetal asphyxia Am J Obstet Gynecol 1996;175:843-6. 24. Rosen MG. Dickinson JC. The paradox of electronic fetal monitoring: more data may not enable us to predict or prevent infant neurologic morbidity. Am J Obstet Gynecol 1993;168:745-51. 25. Nelson KB, Dambrosia JM, Ting TY, Grether JK. Uncertain value of electronic fetal monitoring in predicting cerebral palsy. N Engl J Med 1996;334:613-8.
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Discussion DR JOHN GIANOPOULOS, Maywood, Illinois. The discipline of obstetrics in the current environment in the United States has been under siege by plaintiffs’ attorneys and the public at large criticizing obstetric care and assessing arguments of causality for poor neurologic outcomes in neonates attributed to care rendered at the time of delivery. There have been multiple litigations across the country that have resulted in significant financial awards being given to patients, with the resultant 30% fee to the plaintiffs’ attorneys, with obstetric care blamed for poor outcomes. We as a discipline have been partially responsible for this dilemma. The concepts of fetal heart rate monitoring and umbilical blood gas measurements have been used as ammunition to fight the battle against obstetricians in the provision of obstetric care, with claims of significant injury because of events at or around the time of a child’s birth without sufficient data to support these claims. It is now well known from cerebral palsy literature that most (90%) handicaps incurred in the newborn period are related to events that occur antenatally, before the onset of the intrapartum period, or in the immediate neonatal period. Approximately 10% of neonatal handicaps caused by asphyxial injury may be directly attributed to intrapartum events. We, as a discipline, are looking to find scientific, quantifiable data to defend ourselves against accusations of causality for neurologic handicaps resulting from care rendered at the time of labor. The concept of assessing components of neonatal blood to retrospectively assess timing of neonatal injury is not a new one. Naeye and Localio1 first reported in November of 1995 the concept of neonatal lymphocytes and red blood cell normoblasts (ie, nucleated red blood cells) as potential markers for timing of hypoxic insult. Korst et al2 and Phelan et al3, 4 have multiple citations in the literature, with nucleated red blood cells used as a potential marker for neonatal brain injury. In the presence of a hypoxic insult, fetal erythropoietin is released and stimulates the early release of red blood cells from the bone marrow to increase hematocrit and increase the oxygen-carrying capacity of the blood. Animal data suggest that nucleated red blood cells do not occur in the fetal circulation until 48 to 72 hours after a hypoxically stimulated event and remain for approximately 7 days. However, the time course for fetal hypoxia to increased nucleated red blood cell count in the human fetus is unknown. It has been postulated that an elevated level of nucleated red blood cells found in the neonatal period in the first 12 hours of life is correlated with hypoxic events 48 to 72 hours before the time of birth and that elevated nucleated red blood cells in the immediate newborn period may be used as a marker to signify that the events that led to the neonatal injury occurred before labor and may be used defensively in litigation to objectively and quantitatively time neonatal injury remote from the time of delivery. Phelan et al3 showed that the highest level of nucleated red blood cells was found in infants born with classical signs of asphyxia and that the level of nucleated red
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blood cells tended to correlate with the timing of fetal neurologic injury. Korst et al2 reported the follow-up of their continuing studies and concluded that increased nucleated red blood cells does identify the presence of fetal asphyxia, and distinct nucleated red blood cell patterns may be helpful in relating to the timing of injury. The authors have presented an interesting assessment of nucleated red blood cells as a potential marker for antepartum intrauterine fetal events that may lead to neurologic injury, producing early neonatal seizures. The authors chose early-onset neonatal seizures as a marker for fetal neurologic injury and asphyxial events. Early neonatal seizures have been implicated, with a high level of correlation with long-term cerebral palsy. The authors used a retrospective approach correlating elevated nucleated red blood cells in patients with early-onset neonatal seizures and matching them to control patients without neonatal seizures. Patients with intrauterine growth restriction, diabetes mellitus, and prematurity were excluded from the eligibility criteria because all three of these conditions have been associated with elevated levels of neonatal nucleated red blood cells. The authors found that those patients with early-onset neonatal seizures had a significantly increased level of nucleated red blood cells compared with neonates without early-onset seizures and concluded that their data may support the hypothesis that neurologic injury leading to early-onset seizures often occurs before the intrapartum period. I believe that the results are clearly presented and the conclusions are well founded, given the data presented. However, I do have some concerns with the data and conclusions drawn. First, the authors assume that nucleated red blood cells indicate the time of neurologic injury to be between 48 hours and 7 days before delivery. However, the data that associate the exact time course from fetal hypoxia to increased nucleated red blood cell count are unknown in human beings and are based on animal studies. Did you carefully review the animal data? How strongly can we associate animal data to our human experience? Of the 30 patients with early-onset neonatal seizures, there was a significantly lower umbilical artery pH, a mean of 7.15 in the early-onset seizure group versus a mean of 7.31 in the control group. When the data are analyzed for those patients with a normal nucleated red blood cell count versus those patients with an elevated nucleated red blood cell count in the early-onset seizure group, the level of umbilical artery pH <7.0 was not significant in either category. It would be interesting to know what the mean umbilical artery pH levels were in each of the 2 groups. If the umbilical artery pH was significantly depressed in the normal nucleated red blood cell group versus the elevated nucleated red blood cell group leading to earlyonset seizures, one may be able to postulate that those patients with a normal nucleated red blood cell count who had early-onset seizures did experience a significant acute asphyxial event leading to lower umbilical artery pH levels. Therefore was there a difference in the mean umbilical artery pH in the early-onset seizure group with
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a normal nucleated red blood cell count versus the earlyonset seizure group that had an elevated nucleated red blood cell count? The authors state that it is difficult to prove in an individual case that the primary insult did not occur during the intrapartum period. This may be true; however, I contend that, with our entire armamentarium of umbilical blood gas data, the absence or presence of nucleated red blood cells in neonatal blood, the absence or presence of lymphocytes in neonatal blood, and fetal heart rate monitor patterns in an objective, evidence-based manner with ethical expert witnesses reviewing both sides for plaintiff and physician, the dilemma of causality and assessing blame on intrapartum care may be reduced. I believe that the authors should be complemented on a very well done piece of work. It supports earlier findings and adds to our knowledge in the literature. My last recommendation to the authors is that they de-emphasize the strength of their findings. They conclude that the findings support the hypothesis that nucleated red blood cells may be used in timing neonatal injury. However, because it is not known from human data the exact timing of the injury and the timing is inferred from animal data, I believe a less strong statement, such as “our findings may be suggestive or are potentially supportive of this hypothesis,” may be more appropriate, because this work will likely serve as supportive literature in closing arguments in courtrooms around the United States. REFERENCES
1. Naeye RL, Localio AR. Timing hypoxemic brain damage. Obstet Gynecol 1995;86:718-9. 3. Phelan JP, Ahn, MO, Korst LM, Martin GI. Nucleated red blood cells: a marker for fetal asphyxia? Am J Obstet Gynecol 1995;173:1380-4. 2. Korst LM, Phelan JP, Ahn MO, Martin GI. Nucleated red blood cells: an update on the marker for asphyxia. Am J Obstet Gynecol 1996;175:843-6. 4. Phelan JP, Korst LM, Ahn MO, Martin GI. Neonatal nucleated red blood cell and lymphocyte counts in fetal brain injury. Obstet Gynecol 1998;91:485-9.
DR ROBERT CARPENTER, Houston, Texas. One other marker that has been used for true intrapartum asphyxia is creatine phosphokinase isoenzymes and BB fraction. Some units will routinely use that in such babies. Does your unit do that? Do you have any potential data that could be analyzed? UNIDENTIFIED SPEAKER. Were any data available in this review that examined the placentas that should also be evaluated and perhaps used to time the injury? DR PAT COLLINS, Maywood, Illinois. The early-onset seizure data and the cases were presented as both clinical and electroencephalographic data. Clinical diagnosis of seizures in a newborn is notoriously difficult. What proportion of data was clinically based versus obtained by means of electroencephalography? The data were presented as a ratio of nucleated red blood cells to the white blood cell count and as a standardization to the white blood cell count. Were the white blood cell counts in the control neonates and the cases similar?
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DR WILLIAM P. GIDEON, Norman, Oklahoma. On the electroencephalograms, was any analysis done for localization? Was any family history extracted for history of epilepsy, mental retardation, or degenerative neurologic disorders? Was any scanning performed that might have also shown anatomic defects as a cause of the seizure activity? DR BLACKWELL (Closing). Neurologic injury in term fetuses is unfortunately an area that we do not know nearly enough about. Why certain fetuses are able to tolerate certain events whereas others readily decompensate is beyond our current understanding. One of the inherent problems is that in many cases fetal injury is not recognized immediately. It may be 12 to 24 hours before profound neonatal symptoms develop, and, depending on who is attending the delivery (perinatologist, general obstetrician, family practitioner, or midwife) and where it occurs (tertiary care hospital, community hospital), tests such as umbilical cord blood analysis and placental pathologic study may not be routinely performed. Even in university-based tertiary care centers such as ours, these studies are at times absent in cases with adverse fetal outcomes. A second problem is that fetal injury at term is an infrequent, often predictable event. These two facts together make it quite difficult to conduct clinical studies. That is why we were essentially relegated to performing this type of retrospective study. So, even in the best of circumstances, for many patients we were unable to get a clear idea of the pathophysiologic condition involved. In the medicolegal arena clinicians are often left with-
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out an umbilical pH level for exclusion of intrapartum acidemia or placental evidence of chronic prenatal disease, and experts, even outside of the courtroom, will disagree about the clinical significance of various fetal heart rate patterns. This is why the neonatal nucleated red blood cell count, as a measure for the timing of the onset of in utero hypoxic ischemia, is an attractive diagnostic tool. The entry criterion for the study was the presence of seizures by either clinical or electroencephalographic means. In fact, all neonates had both. The clinical diagnosis of seizure was taken from notations in the neonatal medical record by the neonatologist, pediatrician, or nurse practitioner. We did not analyze various aspects of the electroencephalogram. Patients were excluded if there was a maternal history of a seizure disorder; however, the presence or absence of a family history of epilepsy was not described in the charts. We also excluded patients if there was a structural fetal defect detected by prenatal ultrasonography. In this analysis we did not include placental examination, although we are currently in the process of this work. Even in the best of circumstances, if one is able to put together the fetal heart rate pattern, umbilical cord pH at delivery, neonatal nucleated red blood cell count, and neuroimaging studies of injured neonates, I am not exactly certain whether it will be possible to come up with a clear explanation or obvious pattern of causation. The final episode of brain injury may be a result of a combination or synergy of various factors, with each fetus having a different threshold.