- Email: [email protected]
The effect of presentation and mode of delivery on neonatal outcome in the second twin
The effect of presentation and mode of delivery on neonatal outcome in the second twin Phillip C. Greig, MD: Jean-Claude Veille, MD,a Timothy Morgan, PhD," and Linda Henderson, RNa Winston-Salem, North Carolina OBJECTIVE: The purpose of this study was to determine if cesarean delivery of the nonvertex second twin improved neonatal outcome. STUDY DESIGN: We examined the maternal and neonatal records from 457 sets of twins delivered from 1985 to 1990. We compared 1- and 5-minute Apgar scores, umbilical artery and vein blood pH values, duration of neonatal hospitalization, the incidence and length of ventilation, intraventricular hemorrhage, birth trauma, and mortality rate between vertex and nonvertex second twins delivered either vaginally or by cesarean section. RESULTS: The presentation and mode of delivery of the second twin was not associated with a significant difference in any of the outcome variables except for the 1-minute Apgar score, which was lower in the nonvertex group delivered vaginally. CONCLUSION: Our data do not support routine cesarean delivery for twins of any birth weight when the second twin is nonvertex. (AM J OSSTET GVNECOL 1992;167:901-6.)
Key words: Twins, delivery, umbilical blood gases, birth order Twin gestations make up approximately 1% of all pregnancies. I These pregnancies are at a higher risk than singletons for perinatal morbidity and mortality." The greatest danger exists for the second twin, especially those in a nonvertex position.'" 4 These considerations have led to an increased number of cesarean deliveries performed in twin pregnancies. Rydhstrom" reported an increase in the cesarean section rate in Europe from 8% in 1973 to 69% in 1983. Bell et al." noted a similar increase in the United States from 3% in 1972 to 51 % in 1984." Vertex-vertex twins have been shown to be safely delivered vaginally at any gestational age.' Recommendations regarding delivery of the vertex-nonvertex presentation are not so clear. Some studies advocate cesarean section for all twins with malpresentation of the second fetus regardless of fetal weight. s . g Others have recommended cesarean delivery for twins with such a presentation only when the fetal weight is estimated to be < 1500 to 2000 gm. IO • II Bell et al. 6 and Rydhstrom et al. 12 . 13 in more recent studies failed to show that cesarean section improved neonatal outcome in twin pregnancies in any weight group. Much of the earlier data were collected before 1975, From the Department of Obstetrics and Gynecology" and the Department of Public Health Sciences,' Bowman Gray School of Medicine of Wake Forest University. Presented at the Twelfth Annual Meeting of the Society of Perinatal Obstetricians, Orlando, Florida, February 3-8, 1992. Reprint requests: Phillip C. Greig, MD, Department of Obstetrics and Gynecology, Bowman Gray School of Medicine (BGSM), WinstonSalem, NC 27157. 6/6/39913
when external fetal monitoring and ultrasonography were not routinely performed. According to Farooqui et al.,2 50% of the twins in their study were not diagnosed until labor began and 30% were discovered only after delivery of the first twin. Taylor" concluded in 1976 that cesarean section was the better mode of delivery for all nonvertex twins. The purpose of this study was to examine twin pregnancies in the context of modern obstetrics and neonatalogy to determine if the mode of delivery of the second nonvertex twin was related to neonatal outcome. Material and methods
The labor and delivery records at Forsyth Memorial Hospital were reviewed for all twin deliveries between Jan. 1, 1985, and Dec. 31, 1990. This is the obstetric teaching hospital for Bowman Gray School of Medicine and the only obstetric hospital in Forsyth County. There were 457 sets of twins out of 31,509 deliveries for an incidence of 1.5%. The maternal and neonatal charts for all of the twin deliveries were then examined. A number of these patients were out-of-county maternal transfers. The twin cesarean section rate remained relatively constant over the study period at 45% to 47%. All twin pregnancies were cared for and delivered by maternal-fetal medicine faculty, private obstetricians, and residents supervised by the faculty. Forty-one sets of twins were excluded for the following reasons: (1) an estimated gestational age <24 completed weeks as derived from the date of the last menstrual period and ultrasonography data, (2) birth weight <500 gm, (3) a 901
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4000
o Non-vertex
/ Cesarean / Vaginal Fa Vertex / Cesarean • Vertex / Vaginal
mNon-vertex 3000
n=149 n=114
n=77 Grams 2000 n=76 1000
0
500-1499
1500-1999 2000-2499 Weight Categories (grams)
~2500
p Value not significant in all four weight categories. Number of neonates in each group is shown above corresponding bar and n = number of neonates in each weight category. Fig. l. Comparison between mean birth weights within each presentation-delivery group.
documented intrauterine fetal death occurring before labor, (4) lethal anomalies diagnosed prenatally, (5) monoamniotic twins diagnosed prenatally, (6) twins delivered by emergency cesarean section because of abruptio placentae or fetal distress, and (7) twins who received surfactant after delivery. A total of 416 sets of twins were then analyzed for the following neonatal outcome variables: (1) Apgar scores at 1 and 5 minutes, (2) umbilical cord blood pH from both the artery and the vein, (3) significant birth trauma defined as any fracture or nerve palsy that occurred during delivery; (4) neonatal days in the hospital; (5) incidence of intubation and length of time on assisted ventilation (includes continuous positive airway pressure), (6) incidence of severe (grade 3 or 4) intraventricular hemorrhage documented by head ultrasonography done routinely at 3 to 7 days of life in all neonates < 1500 gm and/or 34 weeks' gestation, (7) neonatal deaths that occurred after delivery but before discharge from the hospital. The second twins were divided into four presentation-delivery groups. The first two groups were those second twins in non vertex presentations delivered vaginally or by cesarean section. The second two groups were those second twins in vertex presentations delivered vaginally or by cesarean section. The non vertex groups include fetuses in breech or transverse presentation. These four presentation-delivery groups of second twins are compared throughout the analysis. To evaluate the twins for possible differences among the presentation-delivery groups, the continuous outcome variables were analyzed by means of analysis of covariance and the dichotomous outcome variables were analyzed with Fisher's exact test, X2, and MantelHaenszel X2 methods. The ordered Apgar score cate-
gories were analayzed by the Kruskal-Wallis rank sum test. Outcome measures were compared between groups with birth weight or gestational age used as a covariate or stratification factor. The results were similar when gestational age or birth weight was therefore controlled for; results are presented with birth weight controlled for. To avoid missing any possible differences in the lower birth weight groups because of the greater number of twins in the larger birth weight groups, we analyzed the data in four weight categories: 500 to 1499, 1500 to 1999, 2000 to 2499, and :=::2500 gm. Neonatal sex and race were also included in the analysis as covariates. Neonates who died were not included in the analysis of neonatal hospital stay or length of time of assisted ventilation. A value of p < 0.05 was considered statistically significant. Umbilical cord blood was obtained in 3 ml heparinized plastic syringes immediately after delivery, placed on ice, and taken promptly to the hospital blood gas laboratory for analysis.
Results The mean values of the birth weights in each of the presentation-delivery groups were analyzed to determine if the groups were comparable (Fig. 1). There was no significant mean birth weight difference found between the four presentation-delivery groups within each birth weight category. The 1- and 5-minute mean Apgar scores of the four presentation-delivery groups are shown in Table I. Within the four weight categories, only breech fetuses >2500 gm delivered vaginally had a significantly lower I-minute Apgar score when compared with the other three presentation-delivery groups. The 5-minute Apgar scores were not significantly different among the
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Table I. Mean Apgar scores at I and 5 minutes of second twins by birth weight groups, presentation, and mode of delivery Weight group 500-1499 gm Mean 1 min Apgar score
Nonvertex Cesarean Vaginal Vertex Cesarean Vaginal Kruskal-Wallis P Value
Mean 5 min Apgar score
1500-1999 gm Mean 1 min Apgar score
Mean 5 mill Apgar score
2000-2499 gm Mean 1 min Apgar score
?2500 gm
Mean 5 min Apgar score
Mean 1 min Apgar score
Mean 5 min Apgar score
4.8 2.4
6.8 5.2
6.1 5.3
7.8 8.5
7.1 6.3
8.6 8.2
7.5 6.3
8.8 8.7
2.8 4.1
4.4 6.3
6.6 6.8
8.5 8.5
6.8 6.9
8.6 8.7
7.8 7.2
8.9 8.6
0.06
0.11
0.28
0.34
0.61
0.70
0.02
0.30
four presentation-delivery groups in all four weight categories. In 52% of the neonates, umbilical artery blood, umbilical venous blood, or both were available for pH analysis. No significant differences in the venous or arterial mean blood pH values were found among the four different presentation-delivery groups within each of the weight categories (Fig. 2). Neonatal hospital stay was analyzed after maternal hospital stay was corrected for by subtracting maternal hospital days from neonatal hospital days. There was no significant difference in the number of days the neonate was hospitalized among the four presentationdelivery groups. The incidence of intubation after delivery and the length of time on assisted ventilation were used to define the occurrence and severity of neonatal respiratory distress syndrome. No significant difference in the proportion of infants intubated or the length of time ventilated was found among the four presentation-delivery groups within each of the weight categories as seen in Fig. 3. However, the mean number of hours ventilated in the 1500 to 1999 gm weight category was greater for both of the nonvertex groups. There was no significant difference in the mean number of hours ventilated between nonvertex fetuses born vaginally and non vertex fetuses born by cesarean section. Eleven cases of severe intraventricular hemorrhage were distributed among three of the four presentationdelivery groups (Table II). There Was not a significant difference in the incidence of intraventricular hemorrhage among these groups. There were no hemorrhages in the nonvertex vaginal delivery group. There was only one case of significant birth trauma among the 457 sets of twins delivered. A term infant had a fracture of the humerus during a breech ex-
traction. This infant had Apgar scores of 7 and 8 at I and 5 minutes. The umbilical cord blood pH values were 7.24 from the artery and 7.30 from the vein. The child went home 3 days after the delivery with its mother. Follow-up showed that the arm healed without complication. There was not a single case of head entrapment found in the 63 nonvertex fetuses delivered vaginally. Mortality was not significantly different among the four presentation-delivery groups within each birth weight category. Eighteen external or internal versions were attempted. Of the 16 external versions, 10 were successful (63%) in converting the breech or transverse fetuses to a vertex presentation with subsequent vaginal delivery. Of the six failures, three were delivered by vaginal breech extraction and three required cesarean section. Ofthe two internal podalic versions, one was successful, resulting in a breech vaginal delivery, whereas the other fetus requirtd a cesarean section. The 18 neonates that underwent attempted version, either successful or unsuccessful, were compared with those non vertex infants that underwent cesarean section together with the first twin (n = 119). There was no significant difference in any of the outcome variables except for lower I-minute Apgar scores in the version group. The cesarean section rate for fetuses undergoing version was only 22%. The version attempts were distributed throughout all weight categories, and success was not related to fetal size. A separate analysis of the data was done to exclude twins with complications not related to delivery but possibly affecting outcome. These were pregnancies with a birth weight discordance >20% or a significant congenital anomaly not diagnosed prenatally. Twins with prenatally diagnosed congenital anomalies had already been excluded in the original analysis. This second ex-
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MEAN UMBILICAL VEIN pH
7.40 7.30 7.20 7.10
o Non-vertex
7.00
DO II
MEAN UMBILICAL ARTERY pH
7.40
•
/ Cesarean Non-vertex / Vaginal Vertex / Cesarean Vertex / Vaginal
7.30 7.20 7.10 7.00
500-1499
1500-1999 2000-2499 Weight Categories (grams)
~2500
Fig. 2. Mean umbilical artery and vein blood pH comparison among four presentation-delivery groups. p Value not significant in all four weight categories.
500
Mean Hours
o Non-vertex
400
/ Cesarean lID Non-vertex / Vaginal II Vertex / Cesarean • Vertex / Vaginal
300
•
p~O.05 for Non-Vertex Twins compared to Vertex Twins
200 100
o
500-1499
1500-1999
2000-2499
~2500
Weight Categories (grams) Fig. 3. Comparison of length of ventilation required by each presentation-delivery group.
c1usion involved 13 pairs of twins. There were no differences in the results after these exclusions on comparison with the results in the original analysis. Twenty-six combination deliveries occurred in which a vaginal delivery of the first twin was performed and the second was delivered by cesarean section. This was due to cord prolapse in 14 pairs and persistent malpresentation in 12. Internal podalic and external cephalic versions were not attempted in all of these cases. All of the outcome variables of the group of second twins requiring emergency cesarean section were compared with those of non vertex second twins undergoing routine cesarean delivery together with the first twin. There were no significant differences in the outcome
variables except for lower I-minute Apgar scores in the combination deliverv group.
Comment No difference exists in intrapartum morbidity or mortality in twins compared with singletons when prematurity is controlled for. 14. IS For cases in which the first twin is in vertex presentation and the second is nonvertex, there are no published data from the last 15 years to support automatic cesarean delivery regardless of the estimated fetal weight. "Prior to 1970, standard obstetrical practice was management of twin labor according to the presentation of the first twin, with delivery maneuvers appropriate to deliver the sec-
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Table II. Incidence of grade ::::::3 intraventricular hemorrhage (n Presentation-delivery group
Nonvertex Cesarean Vaginal Vertex Cesarean Vaginal
11)
No. of cases 0(' intraventricular hemorrhage
No. of neonates in each group
6
145
63
o
2 3
79 129
3
o
p Value
ond twin depending on the presentation."Iti In 1976, Taylor" recommended that to improve neonatal outcome cesarean delivery of all twins should be performed if one was in non vertex presentation. Since then the percentage of twins delivered by cesarean section has increased significantly. With current obstetric technology (electronic fetal monitoring and obstetric ultrasonography), the second twin may be better protected from intrapartum morbidity. Most of the studies showing an increased adverse outcome in the second twin were done at a time when the second twin was not monitored and often not diagnosed until after the delivery of the first twin. This second twin was at a significant disadvantage. Previous studies have shown vaginal breech babies to have lower I-minute Apgar scores. I, We found this true only in the nonvertex vaginal group >2500 gm. There was not a significant difference among the four presentation-delivery groups within each weight category for arterial or venous umbilical blood pH. There was no significant difference in the number of days the neonate spent in the hospital, the incidence of intubation, or the number of hours of assisted ventilation. There was only one case of delivery trauma and that was in the nonvertex group during a term breech extraction. The last variable, mortality, was not higher in the nonvertex group of fetuses delivered vaginally when compared with those in the same weight category delivered by cesarean section. Patients with a prenatal diagnosis of a congenital anomaly had been excluded because this diagnosis may have changed the intrapartum management. This meant that we included second twins with tetralogy of Fallot, diaphragmatic hernia, and a dysplastic kidney in our original analysis because they were not diagnosed prenatally. Severely discordant fetuses with birth weight differences >20% may also have affected the results. After the anomalous and discordant fetuses were removed, results did not change in any of the outcome variables. Evrard and Gold I" found significant mortality in the second twin in their small review of combination vaginal and cesarean deliveries. There was no significant in-
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Incidence (7c)
4
2
NS
crease in adverse outcomes in second twins requiring a cesarean delivery after vaginal delivery of the first twin. Most of our patients had epidural anesthesia for delivery, and the cesarean sections were performed promptly and without complication. External and internal versions were found to be safe and effective. These results further encourage attempting vaginal delivery of the nonvertex second twin. There is always the risk of selection bias in a retrospective study. Some in the cesarean group of neonates may have been "sicker" at delivery. To control for this, twins undergoing emergency cesarean section for fetal distress were excluded from all analysis. Selection bias should have favored a better outcome in the group delivered by cesarean section because the more immature fetuses would have been "written off' and allowed to be delivered vaginally. There were >40 maternal-fetal medicine faculty, private obstetricians, and residents who delivered the twins in this study. The patients delivered by the university perinatologist and residents were analyzed separately from the patients delivered by the private obstetricians. There was no significant difference in the percentage of patients delivered by cesarean section (48% vs 49%) between the two groups. There were also no changes in the results of any of the neonatal outcome variable analyses. There is no way to control for the individual physician's skills at vaginal breech delivery, because no single physician delivered enough twins to allow for a statistical analysis. By including such a large number of twins, the selection bias and individual skill level variation should have been minimized. The number of second twins delivered vaginally from the nonvertex presentation in the> 1500 gm groups is sufficient (n = 54) to concur with previous studies that this model of delivery is safe within this weight group.IO. 11. 13 The question of how to manage the nonvertex second twin < 1500 gm still remains. The number of second twins in the < 1500 gm category in the nonvertex presentation group delivered vaginally was small (n = 9). This puts the data at risk of a type II error. On the other hand, nine outcome variables
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Greig et al.
were examined by multiple statistical analysis with the same results showing no relationship between mode of delivery and outcome in the non vertex second twin. There were also no cases of head entrapment out of 21 fetuses <2000 gm delivered vaginally from a nonvertex presentation. There have been many recent studies looking at the best mode of delivery for the premature, nonvertex second twin. The study by Adam et al. 19 of twins included 17 non vertex second twins between 1000 and 1499 gm delivered vaginally. There was no significant difference in neonatal morbidity or mortality between the vaginally delivered and cesarean groups. Davison et al. 20 recently published an article on 54 second twins delivered by breech extraction who weighed between 750 and 2000 gm. They found no difference in neonatal morbidity or morality when the vaginal breechdelivered group was compared with a cesarean group. They also had no cases of head entrapment in these premature breech fetuses delivered vaginally. Fishman et al. 21 compared 183 vaginally delivered non vertex second twins with 207 vaginally deilivered vertex second twins >20 weeks' gestation to term. Specific weight group data were not given, but after stratifying for birth weight there was no significant difference in any of the neonatal outcome variables examined. The data from our current study along with the results from these others make a convincing argument as to the safety of vaginal delivery for the nonvertex second twin <2000 gm. These data indicate the need to reassess the currently prevailing management of twin pregnancies with a nonvertex second twin. The results from this study do not support routine abdominal delivery when the second twin is in the non vertex presentation. I thank Melissa Swain for her help in this study. REFERENCES I. Benirschke K. Multiple gestation: incidence, etiology and inheritance. In: Creasy RK, Resnik R, eds. Maternal-fetal medicine: principles and practice. Philadelphia: WB Saunders, 1989:565-79. 2. Farooqui M, Grossman]H, Shannon RA. A review oftwin pregnancy and perinatal mortality. Obstet Gynecol Surv 1973;28:144-53.
October 1992 Am J Obstet Gynecol
3. Ware HH. The second twin. AM ] OBSTET GYNECOL 1971; I 10:865-73. 4. Verduzco RD, Rosario R, Rigatto H. Hyaline membrane disease in twins: a 7 year review with a study on zygosity. AM] OBSTET GYNECOL 1976;125:668-71. 5. Rydhstrom H. Prognosis for twins with birth weight < 1500 gm: the impact of cesarean section in relation to fetal presentation. AM] OBSTET GYNECOL 1990; 163:52833. 6. Bell D, Johansson D, McLean FH, Usher RH. Birth asphyxia, trauma, and mortality in twins: has cesarean improved outcome? AM ] OBSTET GYNECOL 1986;154: 235-9. 7. Chervenak F. The controversy of mode of delivery in twins: the intrapartum management of twin gestation (part II). Semin Perinatol 1986; 10:44-9. 8. Cetrulo CL. The controversy of mode of delivery in twins: the intrapartum management of twin gestation. Semin PerinatoI1986;10:39-43. 9. Taylor ES. Editorial. Obstet Gynecol Surv 1976;31: 535-6. 10. Barrett]M, Staggs SM, Van Hooydonk]E, Growdon]H, Killam AP, Boehm FH. The effect of type of delivery upon neonatal outcome in premature twins. AM] OBSTET GyNECOL 1982;143:360-7. II. Trofatter KF. Management of delivery. Clin Perinatol 1988; 15:93- 106. 12. Rydhstrom H, Ingemarsson I, Ohrlander S. Lack of correlation between a high cesarean section rate and improved prognosis for low birth weight twins «2500 g). BrJ Obstet Gynaecol 1990;97:229-33. 13. Rydhstrom H, Ingemarsson 1. A case-control study of the effects of birth by cesarean section on intrapartum and neonatal mortality among twins weighing 1500-2499 g. Br] Obstet Gynaecol 1991 ;98:249-53. 14. Ho SK, Wu P. Perinatal factors and neonatal morbidity in twin pregnancy: perinatal factors and neonatal morbidity in twin pregnancy. AM ] OBSTET GYNECOL 1973; 122:979-87. 15. McCarthy B], Sachs BP, Layde PM. The epidemiology of neonatal death in twins. AM ] OBSTET GYNECOL 1981;141:252-6. 16. Waren ski lC, Kochenour NK. Intrapartum management of twin gestation. Clin Perinatol 1989; 16:889-97. 17. Eskes TK, Timmer LA, ]ongsma K, ]ongsma HW. The second twin. Eur ] Obstet Gynecol Reprod Bioi 1984;19: 159-66. 18. Evrard], Gold E. Cesarean section for delivery of the second twin. Obstet GynecoI1981;57:581-3. 19. Adam C, Allen AC, Baskeh TF. Twin delivery: influence of the presentation and method of delivery on the second twin. AM] OBSTET GYNECOL 1991;165:23-7. 20. Davison L, Easterling TR, Jackson ]C, Benedetti TJ. Breech extraction of low-birth-weight second twins: can cesarean section be justified? AM ] OBSTET GYNECOL 1992; 166:497-502. 21. Fishman A, Grubb D, Kovacs B. Vaginal delivery of the non-vertex second twin [Abstract]. AM] OBSTET GYNECOL 1992;166:287.
Key words: Twins, delivery, umbilical blood gases, birth order Twin gestations make up approximately 1% of all pregnancies. I These pregnancies are at a higher risk than singletons for perinatal morbidity and mortality." The greatest danger exists for the second twin, especially those in a nonvertex position.'" 4 These considerations have led to an increased number of cesarean deliveries performed in twin pregnancies. Rydhstrom" reported an increase in the cesarean section rate in Europe from 8% in 1973 to 69% in 1983. Bell et al." noted a similar increase in the United States from 3% in 1972 to 51 % in 1984." Vertex-vertex twins have been shown to be safely delivered vaginally at any gestational age.' Recommendations regarding delivery of the vertex-nonvertex presentation are not so clear. Some studies advocate cesarean section for all twins with malpresentation of the second fetus regardless of fetal weight. s . g Others have recommended cesarean delivery for twins with such a presentation only when the fetal weight is estimated to be < 1500 to 2000 gm. IO • II Bell et al. 6 and Rydhstrom et al. 12 . 13 in more recent studies failed to show that cesarean section improved neonatal outcome in twin pregnancies in any weight group. Much of the earlier data were collected before 1975, From the Department of Obstetrics and Gynecology" and the Department of Public Health Sciences,' Bowman Gray School of Medicine of Wake Forest University. Presented at the Twelfth Annual Meeting of the Society of Perinatal Obstetricians, Orlando, Florida, February 3-8, 1992. Reprint requests: Phillip C. Greig, MD, Department of Obstetrics and Gynecology, Bowman Gray School of Medicine (BGSM), WinstonSalem, NC 27157. 6/6/39913
when external fetal monitoring and ultrasonography were not routinely performed. According to Farooqui et al.,2 50% of the twins in their study were not diagnosed until labor began and 30% were discovered only after delivery of the first twin. Taylor" concluded in 1976 that cesarean section was the better mode of delivery for all nonvertex twins. The purpose of this study was to examine twin pregnancies in the context of modern obstetrics and neonatalogy to determine if the mode of delivery of the second nonvertex twin was related to neonatal outcome. Material and methods
The labor and delivery records at Forsyth Memorial Hospital were reviewed for all twin deliveries between Jan. 1, 1985, and Dec. 31, 1990. This is the obstetric teaching hospital for Bowman Gray School of Medicine and the only obstetric hospital in Forsyth County. There were 457 sets of twins out of 31,509 deliveries for an incidence of 1.5%. The maternal and neonatal charts for all of the twin deliveries were then examined. A number of these patients were out-of-county maternal transfers. The twin cesarean section rate remained relatively constant over the study period at 45% to 47%. All twin pregnancies were cared for and delivered by maternal-fetal medicine faculty, private obstetricians, and residents supervised by the faculty. Forty-one sets of twins were excluded for the following reasons: (1) an estimated gestational age <24 completed weeks as derived from the date of the last menstrual period and ultrasonography data, (2) birth weight <500 gm, (3) a 901
902
Greig et al.
October 1992 Am J Obstet Gynecol
4000
o Non-vertex
/ Cesarean / Vaginal Fa Vertex / Cesarean • Vertex / Vaginal
mNon-vertex 3000
n=149 n=114
n=77 Grams 2000 n=76 1000
0
500-1499
1500-1999 2000-2499 Weight Categories (grams)
~2500
p Value not significant in all four weight categories. Number of neonates in each group is shown above corresponding bar and n = number of neonates in each weight category. Fig. l. Comparison between mean birth weights within each presentation-delivery group.
documented intrauterine fetal death occurring before labor, (4) lethal anomalies diagnosed prenatally, (5) monoamniotic twins diagnosed prenatally, (6) twins delivered by emergency cesarean section because of abruptio placentae or fetal distress, and (7) twins who received surfactant after delivery. A total of 416 sets of twins were then analyzed for the following neonatal outcome variables: (1) Apgar scores at 1 and 5 minutes, (2) umbilical cord blood pH from both the artery and the vein, (3) significant birth trauma defined as any fracture or nerve palsy that occurred during delivery; (4) neonatal days in the hospital; (5) incidence of intubation and length of time on assisted ventilation (includes continuous positive airway pressure), (6) incidence of severe (grade 3 or 4) intraventricular hemorrhage documented by head ultrasonography done routinely at 3 to 7 days of life in all neonates < 1500 gm and/or 34 weeks' gestation, (7) neonatal deaths that occurred after delivery but before discharge from the hospital. The second twins were divided into four presentation-delivery groups. The first two groups were those second twins in non vertex presentations delivered vaginally or by cesarean section. The second two groups were those second twins in vertex presentations delivered vaginally or by cesarean section. The non vertex groups include fetuses in breech or transverse presentation. These four presentation-delivery groups of second twins are compared throughout the analysis. To evaluate the twins for possible differences among the presentation-delivery groups, the continuous outcome variables were analyzed by means of analysis of covariance and the dichotomous outcome variables were analyzed with Fisher's exact test, X2, and MantelHaenszel X2 methods. The ordered Apgar score cate-
gories were analayzed by the Kruskal-Wallis rank sum test. Outcome measures were compared between groups with birth weight or gestational age used as a covariate or stratification factor. The results were similar when gestational age or birth weight was therefore controlled for; results are presented with birth weight controlled for. To avoid missing any possible differences in the lower birth weight groups because of the greater number of twins in the larger birth weight groups, we analyzed the data in four weight categories: 500 to 1499, 1500 to 1999, 2000 to 2499, and :=::2500 gm. Neonatal sex and race were also included in the analysis as covariates. Neonates who died were not included in the analysis of neonatal hospital stay or length of time of assisted ventilation. A value of p < 0.05 was considered statistically significant. Umbilical cord blood was obtained in 3 ml heparinized plastic syringes immediately after delivery, placed on ice, and taken promptly to the hospital blood gas laboratory for analysis.
Results The mean values of the birth weights in each of the presentation-delivery groups were analyzed to determine if the groups were comparable (Fig. 1). There was no significant mean birth weight difference found between the four presentation-delivery groups within each birth weight category. The 1- and 5-minute mean Apgar scores of the four presentation-delivery groups are shown in Table I. Within the four weight categories, only breech fetuses >2500 gm delivered vaginally had a significantly lower I-minute Apgar score when compared with the other three presentation-delivery groups. The 5-minute Apgar scores were not significantly different among the
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903
Table I. Mean Apgar scores at I and 5 minutes of second twins by birth weight groups, presentation, and mode of delivery Weight group 500-1499 gm Mean 1 min Apgar score
Nonvertex Cesarean Vaginal Vertex Cesarean Vaginal Kruskal-Wallis P Value
Mean 5 min Apgar score
1500-1999 gm Mean 1 min Apgar score
Mean 5 mill Apgar score
2000-2499 gm Mean 1 min Apgar score
?2500 gm
Mean 5 min Apgar score
Mean 1 min Apgar score
Mean 5 min Apgar score
4.8 2.4
6.8 5.2
6.1 5.3
7.8 8.5
7.1 6.3
8.6 8.2
7.5 6.3
8.8 8.7
2.8 4.1
4.4 6.3
6.6 6.8
8.5 8.5
6.8 6.9
8.6 8.7
7.8 7.2
8.9 8.6
0.06
0.11
0.28
0.34
0.61
0.70
0.02
0.30
four presentation-delivery groups in all four weight categories. In 52% of the neonates, umbilical artery blood, umbilical venous blood, or both were available for pH analysis. No significant differences in the venous or arterial mean blood pH values were found among the four different presentation-delivery groups within each of the weight categories (Fig. 2). Neonatal hospital stay was analyzed after maternal hospital stay was corrected for by subtracting maternal hospital days from neonatal hospital days. There was no significant difference in the number of days the neonate was hospitalized among the four presentationdelivery groups. The incidence of intubation after delivery and the length of time on assisted ventilation were used to define the occurrence and severity of neonatal respiratory distress syndrome. No significant difference in the proportion of infants intubated or the length of time ventilated was found among the four presentation-delivery groups within each of the weight categories as seen in Fig. 3. However, the mean number of hours ventilated in the 1500 to 1999 gm weight category was greater for both of the nonvertex groups. There was no significant difference in the mean number of hours ventilated between nonvertex fetuses born vaginally and non vertex fetuses born by cesarean section. Eleven cases of severe intraventricular hemorrhage were distributed among three of the four presentationdelivery groups (Table II). There Was not a significant difference in the incidence of intraventricular hemorrhage among these groups. There were no hemorrhages in the nonvertex vaginal delivery group. There was only one case of significant birth trauma among the 457 sets of twins delivered. A term infant had a fracture of the humerus during a breech ex-
traction. This infant had Apgar scores of 7 and 8 at I and 5 minutes. The umbilical cord blood pH values were 7.24 from the artery and 7.30 from the vein. The child went home 3 days after the delivery with its mother. Follow-up showed that the arm healed without complication. There was not a single case of head entrapment found in the 63 nonvertex fetuses delivered vaginally. Mortality was not significantly different among the four presentation-delivery groups within each birth weight category. Eighteen external or internal versions were attempted. Of the 16 external versions, 10 were successful (63%) in converting the breech or transverse fetuses to a vertex presentation with subsequent vaginal delivery. Of the six failures, three were delivered by vaginal breech extraction and three required cesarean section. Ofthe two internal podalic versions, one was successful, resulting in a breech vaginal delivery, whereas the other fetus requirtd a cesarean section. The 18 neonates that underwent attempted version, either successful or unsuccessful, were compared with those non vertex infants that underwent cesarean section together with the first twin (n = 119). There was no significant difference in any of the outcome variables except for lower I-minute Apgar scores in the version group. The cesarean section rate for fetuses undergoing version was only 22%. The version attempts were distributed throughout all weight categories, and success was not related to fetal size. A separate analysis of the data was done to exclude twins with complications not related to delivery but possibly affecting outcome. These were pregnancies with a birth weight discordance >20% or a significant congenital anomaly not diagnosed prenatally. Twins with prenatally diagnosed congenital anomalies had already been excluded in the original analysis. This second ex-
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MEAN UMBILICAL VEIN pH
7.40 7.30 7.20 7.10
o Non-vertex
7.00
DO II
MEAN UMBILICAL ARTERY pH
7.40
•
/ Cesarean Non-vertex / Vaginal Vertex / Cesarean Vertex / Vaginal
7.30 7.20 7.10 7.00
500-1499
1500-1999 2000-2499 Weight Categories (grams)
~2500
Fig. 2. Mean umbilical artery and vein blood pH comparison among four presentation-delivery groups. p Value not significant in all four weight categories.
500
Mean Hours
o Non-vertex
400
/ Cesarean lID Non-vertex / Vaginal II Vertex / Cesarean • Vertex / Vaginal
300
•
p~O.05 for Non-Vertex Twins compared to Vertex Twins
200 100
o
500-1499
1500-1999
2000-2499
~2500
Weight Categories (grams) Fig. 3. Comparison of length of ventilation required by each presentation-delivery group.
c1usion involved 13 pairs of twins. There were no differences in the results after these exclusions on comparison with the results in the original analysis. Twenty-six combination deliveries occurred in which a vaginal delivery of the first twin was performed and the second was delivered by cesarean section. This was due to cord prolapse in 14 pairs and persistent malpresentation in 12. Internal podalic and external cephalic versions were not attempted in all of these cases. All of the outcome variables of the group of second twins requiring emergency cesarean section were compared with those of non vertex second twins undergoing routine cesarean delivery together with the first twin. There were no significant differences in the outcome
variables except for lower I-minute Apgar scores in the combination deliverv group.
Comment No difference exists in intrapartum morbidity or mortality in twins compared with singletons when prematurity is controlled for. 14. IS For cases in which the first twin is in vertex presentation and the second is nonvertex, there are no published data from the last 15 years to support automatic cesarean delivery regardless of the estimated fetal weight. "Prior to 1970, standard obstetrical practice was management of twin labor according to the presentation of the first twin, with delivery maneuvers appropriate to deliver the sec-
Presentation and delivery of second twin
Volume 167 I'\umber 4, Part I
Table II. Incidence of grade ::::::3 intraventricular hemorrhage (n Presentation-delivery group
Nonvertex Cesarean Vaginal Vertex Cesarean Vaginal
11)
No. of cases 0(' intraventricular hemorrhage
No. of neonates in each group
6
145
63
o
2 3
79 129
3
o
p Value
ond twin depending on the presentation."Iti In 1976, Taylor" recommended that to improve neonatal outcome cesarean delivery of all twins should be performed if one was in non vertex presentation. Since then the percentage of twins delivered by cesarean section has increased significantly. With current obstetric technology (electronic fetal monitoring and obstetric ultrasonography), the second twin may be better protected from intrapartum morbidity. Most of the studies showing an increased adverse outcome in the second twin were done at a time when the second twin was not monitored and often not diagnosed until after the delivery of the first twin. This second twin was at a significant disadvantage. Previous studies have shown vaginal breech babies to have lower I-minute Apgar scores. I, We found this true only in the nonvertex vaginal group >2500 gm. There was not a significant difference among the four presentation-delivery groups within each weight category for arterial or venous umbilical blood pH. There was no significant difference in the number of days the neonate spent in the hospital, the incidence of intubation, or the number of hours of assisted ventilation. There was only one case of delivery trauma and that was in the nonvertex group during a term breech extraction. The last variable, mortality, was not higher in the nonvertex group of fetuses delivered vaginally when compared with those in the same weight category delivered by cesarean section. Patients with a prenatal diagnosis of a congenital anomaly had been excluded because this diagnosis may have changed the intrapartum management. This meant that we included second twins with tetralogy of Fallot, diaphragmatic hernia, and a dysplastic kidney in our original analysis because they were not diagnosed prenatally. Severely discordant fetuses with birth weight differences >20% may also have affected the results. After the anomalous and discordant fetuses were removed, results did not change in any of the outcome variables. Evrard and Gold I" found significant mortality in the second twin in their small review of combination vaginal and cesarean deliveries. There was no significant in-
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4
2
NS
crease in adverse outcomes in second twins requiring a cesarean delivery after vaginal delivery of the first twin. Most of our patients had epidural anesthesia for delivery, and the cesarean sections were performed promptly and without complication. External and internal versions were found to be safe and effective. These results further encourage attempting vaginal delivery of the nonvertex second twin. There is always the risk of selection bias in a retrospective study. Some in the cesarean group of neonates may have been "sicker" at delivery. To control for this, twins undergoing emergency cesarean section for fetal distress were excluded from all analysis. Selection bias should have favored a better outcome in the group delivered by cesarean section because the more immature fetuses would have been "written off' and allowed to be delivered vaginally. There were >40 maternal-fetal medicine faculty, private obstetricians, and residents who delivered the twins in this study. The patients delivered by the university perinatologist and residents were analyzed separately from the patients delivered by the private obstetricians. There was no significant difference in the percentage of patients delivered by cesarean section (48% vs 49%) between the two groups. There were also no changes in the results of any of the neonatal outcome variable analyses. There is no way to control for the individual physician's skills at vaginal breech delivery, because no single physician delivered enough twins to allow for a statistical analysis. By including such a large number of twins, the selection bias and individual skill level variation should have been minimized. The number of second twins delivered vaginally from the nonvertex presentation in the> 1500 gm groups is sufficient (n = 54) to concur with previous studies that this model of delivery is safe within this weight group.IO. 11. 13 The question of how to manage the nonvertex second twin < 1500 gm still remains. The number of second twins in the < 1500 gm category in the nonvertex presentation group delivered vaginally was small (n = 9). This puts the data at risk of a type II error. On the other hand, nine outcome variables
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were examined by multiple statistical analysis with the same results showing no relationship between mode of delivery and outcome in the non vertex second twin. There were also no cases of head entrapment out of 21 fetuses <2000 gm delivered vaginally from a nonvertex presentation. There have been many recent studies looking at the best mode of delivery for the premature, nonvertex second twin. The study by Adam et al. 19 of twins included 17 non vertex second twins between 1000 and 1499 gm delivered vaginally. There was no significant difference in neonatal morbidity or mortality between the vaginally delivered and cesarean groups. Davison et al. 20 recently published an article on 54 second twins delivered by breech extraction who weighed between 750 and 2000 gm. They found no difference in neonatal morbidity or morality when the vaginal breechdelivered group was compared with a cesarean group. They also had no cases of head entrapment in these premature breech fetuses delivered vaginally. Fishman et al. 21 compared 183 vaginally delivered non vertex second twins with 207 vaginally deilivered vertex second twins >20 weeks' gestation to term. Specific weight group data were not given, but after stratifying for birth weight there was no significant difference in any of the neonatal outcome variables examined. The data from our current study along with the results from these others make a convincing argument as to the safety of vaginal delivery for the nonvertex second twin <2000 gm. These data indicate the need to reassess the currently prevailing management of twin pregnancies with a nonvertex second twin. The results from this study do not support routine abdominal delivery when the second twin is in the non vertex presentation. I thank Melissa Swain for her help in this study. REFERENCES I. Benirschke K. Multiple gestation: incidence, etiology and inheritance. In: Creasy RK, Resnik R, eds. Maternal-fetal medicine: principles and practice. Philadelphia: WB Saunders, 1989:565-79. 2. Farooqui M, Grossman]H, Shannon RA. A review oftwin pregnancy and perinatal mortality. Obstet Gynecol Surv 1973;28:144-53.
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3. Ware HH. The second twin. AM ] OBSTET GYNECOL 1971; I 10:865-73. 4. Verduzco RD, Rosario R, Rigatto H. Hyaline membrane disease in twins: a 7 year review with a study on zygosity. AM] OBSTET GYNECOL 1976;125:668-71. 5. Rydhstrom H. Prognosis for twins with birth weight < 1500 gm: the impact of cesarean section in relation to fetal presentation. AM] OBSTET GYNECOL 1990; 163:52833. 6. Bell D, Johansson D, McLean FH, Usher RH. Birth asphyxia, trauma, and mortality in twins: has cesarean improved outcome? AM ] OBSTET GYNECOL 1986;154: 235-9. 7. Chervenak F. The controversy of mode of delivery in twins: the intrapartum management of twin gestation (part II). Semin Perinatol 1986; 10:44-9. 8. Cetrulo CL. The controversy of mode of delivery in twins: the intrapartum management of twin gestation. Semin PerinatoI1986;10:39-43. 9. Taylor ES. Editorial. Obstet Gynecol Surv 1976;31: 535-6. 10. Barrett]M, Staggs SM, Van Hooydonk]E, Growdon]H, Killam AP, Boehm FH. The effect of type of delivery upon neonatal outcome in premature twins. AM] OBSTET GyNECOL 1982;143:360-7. II. Trofatter KF. Management of delivery. Clin Perinatol 1988; 15:93- 106. 12. Rydhstrom H, Ingemarsson I, Ohrlander S. Lack of correlation between a high cesarean section rate and improved prognosis for low birth weight twins «2500 g). BrJ Obstet Gynaecol 1990;97:229-33. 13. Rydhstrom H, Ingemarsson 1. A case-control study of the effects of birth by cesarean section on intrapartum and neonatal mortality among twins weighing 1500-2499 g. Br] Obstet Gynaecol 1991 ;98:249-53. 14. Ho SK, Wu P. Perinatal factors and neonatal morbidity in twin pregnancy: perinatal factors and neonatal morbidity in twin pregnancy. AM ] OBSTET GYNECOL 1973; 122:979-87. 15. McCarthy B], Sachs BP, Layde PM. The epidemiology of neonatal death in twins. AM ] OBSTET GYNECOL 1981;141:252-6. 16. Waren ski lC, Kochenour NK. Intrapartum management of twin gestation. Clin Perinatol 1989; 16:889-97. 17. Eskes TK, Timmer LA, ]ongsma K, ]ongsma HW. The second twin. Eur ] Obstet Gynecol Reprod Bioi 1984;19: 159-66. 18. Evrard], Gold E. Cesarean section for delivery of the second twin. Obstet GynecoI1981;57:581-3. 19. Adam C, Allen AC, Baskeh TF. Twin delivery: influence of the presentation and method of delivery on the second twin. AM] OBSTET GYNECOL 1991;165:23-7. 20. Davison L, Easterling TR, Jackson ]C, Benedetti TJ. Breech extraction of low-birth-weight second twins: can cesarean section be justified? AM ] OBSTET GYNECOL 1992; 166:497-502. 21. Fishman A, Grubb D, Kovacs B. Vaginal delivery of the non-vertex second twin [Abstract]. AM] OBSTET GYNECOL 1992;166:287.