Is oxytocin the culprit?

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Correspondence

Treatment of patients with severe preeclampsia in the second trimester To the Editors: This letter is in reference to the article entitled "Maternal and perinatal outcome of con~ervative management of severe preeclampsia in mid trimester" by Sibai et al. (AM J 0BSTET GYNECOL 1985; 152:32-7). The authors reported on a retrospective study of maternal and perinatal outcomes based on conservative management of patients who developed severe preeclampsia in the midtrimester (18 to 27 weeks' gestation). They attempted to address the existing controversy between conservative and aggressive treatment of patients with severe preeclampsia in the second trimester. As reviewers for the Oklahoma OB/GYN Journal Club, we encountered several inconsistencies in the study design and data interpretation. First, unclear definitions of inclusion and exclusion criteria permitted confounding variables to enter into the study. For example, 55% of the subjects were listed as having a history of chronic hypertension and/or renal disease. These may represent a source of bias, as Sibai et al. have previously determined that the risks of perinatal morbidity and mortality are significantly increased in patients with prior histories of chronic hypertension. 1 Second, as the authors admit, the retrospective nature of the study limits its validity. However, the problems described above add further limitations to the clinical relevance of the study. Moreover, application of well-defined and rigid inclusion criteria, as well as clear definitions of the disease state, would reduce the number of confounding variables. Third, the mothers of control group infants experienced no medical complications during pregnancy and remained normotensive throughout their gestation. Conclusions with regard to appropriate treatment modality and pregnancy outcomes cannot be drawn by comparing a normotensive control group with a hypertensive study group. Finally, an appropriate control group (patients with midtrimester-onset preeclampsia in whom aggressive therapy was used) is necessary. The authors contend that improved maternal and perinatal outcomes are achieved with aggressive management of severe preeclampsia in the midtrimester. Without this additional control group and a prospective study design, these claims are in no way substantiated. Cecilia Grasinger Gary R. Thurnau, M.D. Department of Obstetrics and Gynecology University of Oklahoma College of Medicine P. 0. Box 26901 Oklahoma City, Oklahoma 73190

REFERENCE l. Sibai BM, Spinnato JA, Watson DL, Hill GA, Anderson GD. Pregnancy outcome in 303 cases with severe preeclampsia. Obstet Gynecol 1984;64:319.

December 15, 1985 Am J Obstet Gynecol

Reply To the Editors: I would like to thank the reviewers of the Oklahoma OB/GYN Journal Club for their critical review of this report. Most of their comments are relevant and valid; however, most of these points have been emphasized in the text of the report. The report describes our experience in management of 60 consecutive patients for whom an attempt was made to prolong gestation. These patients are a heterogenous group that had various forms of prenatal care and management by several physicians in 80 counties in 5 different states. These patients shared a diagnosis of severe preeclampsia in midtrimester as defined in the manuscript. It is common knowledge that patients developing severe preechimpsia this early usually have chronic hypertension and/or underlying renal disease. Hence most such patients will have this diagnosis if kidney biopsies are performed. Consequently, any report on this subject will have to include such patients. With regard to the second comment, we emphasized this point in several places in the manuscript. The use of a large number of patients lends enough credit to the conclusions. Third, the control infants were delivered following high-risk obstetric complications: premature rupture of the membranes and/or premature labor. The emphasis was on selection of cases with infants of similar gestational age delivered during the same time period that were managed in similar fashion. The "ideal" control group would have been patients with severe preeclampsia presenting in mid trimester who were not "exposed" to prolongation of pregnancy. Given the realities of clinical practice, this almost certainly would have been impossible. Finally, we did not imply that improved perinatal outcome is achieved with aggressive management. We only stated that maternal morbidity will be markedly reduced. I believe that the last three paragraphs in the manuscript are self-explanatory and tend to summarize the findings of this report. BahaM. Sibai, M.D. Division of Maternal/Fetal Medicine Department of Obstetrics and Gynecology The University of Tennessee Center for the Health Sciences 800 Madison Avenue Memphis, Tennessee 38163

Is oxytocin the culprit? To the Editors: It is helpful to at last be able to read the report of the Dublin trial of fetal heart rate monitoring (MacDonald D, Grant A, Sheridan-Pereira M, et al. AM J 0BSTET GYNECOL 1985; 152:524) for we have heard so much about it. Even though I am an advocate of no electronic fetal monitoring in low-risk gravid patients, 1

Correspondence

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we do such monitoring when using oxytocin stimulation, since oxytocin administration is associated with more abnormal fetal heart rate patterns!· 3 I wonder if the authors' institution's use of oxytocin in the auscultation group (no electronic fetal monitoring) might not explain the higher incidence of neonatal seizures in this group? Although the numbers in Table XIV do not seem to add up, nevertheless among the cases with seizures 19 out of 27 (70%) of the mothers without electronic fetal monitoring had received oxytocin compared to only 23% who had oxytocin in the total population! And finally, I would like to ask the authors to estimate what would have been the neonatal results in both groups if cesarean section rather than diffichlt forceps deliveries had been used (three traumatic deaths). Robert C. Goodlin, M.D. Department of Obstetrics and Gynecology University of Colorado Health Sciences Center 4200 East Ninth Avenue Denver, Colorado 80262

REFERENCES 1. Goodlin RC. Low risk obstetric care for low risk mothers. Lancet 1980; 1: 10 17. 2. ToaffME, HezroniJ, ToaffR. Induction oflabor by pharmacological and physiological doses of intravenous oxytocin. Br J Obstet Gynaecol 1978;85:101. 3. Belsky DH. Statistical observations on the elective induction of labor with oxytocin. JAOA 1982;81 :524.

Reply To the Editors:

We thank Dr. Goodlin for his comments. The hypothesis that electronic fetal monitoring reduces the risk of neonatal seizures was generated before our study from the results of previous randomized trials 1 conducted in centers with differing oxytocin policies. This hypothesis was subsequently tested and sustained in the Dublin trial. Secondary analyses stratified for duration of labor and oxytocin use, in contrast, were not prespecified and should be considered only as hypothesis generating. Long labor and oxytocin use are obviously closely linked, and it is not possible to separate them in an analysis of this trial. Oxytocin was used equally (""23%) in the two trial groups. As in cases with labors of >5 hours, neonatal seizures were more common when oxytocin was used. It is very plausible that some of the protective effect of electronic fetal monitoring was against "oxytocin-induced asphyxia." If Dr. Goodlin is suggesting that electronic fetal monitoring is only protective against oxytocin-induced asphyxia, his hypothesis (like others generated from our data) should now be formally tested in further prospective clinical experiments. We would also caution against reading too much into the small number of deaths. Forceps delivery prompted by "failure to advance" was equally common in the two

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trial groups (Table VI), and this was the primary indication for forceps delivery in the three electronic fetal monitoring traumatic deaths. Rotational forceps delivery is never performed at the National Maternity Hospital. Furthermore, the trial cases were consistent with a very large study conducted in the hospital which showed that in only 45% of cases of tentorial tears associated with forceps delivery is the delivery classified as difficult! Nevertheless, we would agree that the extra obstetric intervention by cesarean and forceps delivery prompted by electronic fetal monitoring can have adverse effects on both mothers and babies, and this should be taken into account when considering the role of electronic fetal monitoring in clinical practice. Dermot MacDonald Margaret Sheridan-Pereira Peter Boylan National Maternity Hospital Holles Street Dublin, Ireland Adrian Grant lain Chalmers National Perinatal Epidemiology Unit Radcliffe Infirmary Oxford, England OX2 6HE

REFERENCES 1. Chalmers I. Randomized controlled trials of intrapartum monitoring. In: Thalhammer 0, Baumgarten KV, Pollak A, eds. Perinatal medicine. Stuttgart: Georg Thieme, 1979:260. 2. O'Driscoll K, Meagher D, MacDonald D, Geoghegan F. Traumatic intracranial haemorrhage in first born infants and delivery with obstetric forceps. Br J Obstet Gynaecol 1981;88:577.

Neonatal mortality in very low birth weight and very preterm infants To the Editors:

In their recent paper Goldenberg et al. (Neonatal mortality in infants born weighing 501 to 1000 grams: the influence of changes in birth weight distribution and birth weight-specific mortality rates on neonatal survival. AMJ 0BSTET GYNECOL 1985; 151 :608) rightly drew attention to changes over time in birth weight distribution and their influence on neonatal mortality. It should be pointed out, however, that their definition of neonatal mortality, i.e., "deaths prior to discharge from hospital," causes unnecessary confusion. We believe that the use of the term "neonatal mortality" should, in accordance with the World Health Organization and the International Federation of Gynecologists and Obstetricians; be restricted to death within the first 28 days of life. Similarly, to allow appropriate (inter)national comparisons, birth weight groupings should be consistent with International Federation of Gynecologists and Obstetricians and World Health Organization recommendations and thus be from 500-999 gm rather than 501-1000 gm. Because of the known pref-