Volume 27, Number 2, June 2001
For Breech Births, Cesarean Section Poses Fewer Risks Than Vaginal Delivery
Planned vaginal delivery holds significantly higher risks than planned cesarean section for term infants in breech presentation.1 According to data from a multinational randomized trial, infants scheduled to be delivered by cesarean section are 77% less likely to die and 64% less likely to experience serious neonatal health problems than are those scheduled to be delivered vaginally. The type of delivery planned, however, does not affect the occurrence of serious maternal complications or death.
The analysis included 2,083 women with a term pregnancy who were enrolled at 121 centers in 26 countries around the world between January 1997 and April 2000. Women were eligible to participate in the study if their fetus was in a frank or complete breech presentation.* They were excluded if there was evidence that the fetus was too large to pass through the mother's pelvis, if the fetus was clinically large or weighed 4,000 g or more, if the fetal head was hyperextended, if there was evidence of a fetal anomaly or of any condition that could cause difficulties in delivery, if there was a contraindication to labor or vaginal delivery, or if the fetus had a lethal congenital anomaly. Participating women were randomly assigned to either planned cesarean section or planned vaginal birth.
The 1,041 women allocated to planned cesarean section were scheduled for delivery at 38 weeks of gestation or later. For a variety of reasons, however, 100 women in this group delivered vaginally. Among the 1,042 women allocated to planned vaginal birth, 451 were delivered by cesarean section; these switches occurred primarily because of problems during labor, because of contraindications to vaginal delivery or because of patient or physician preference.
Both groups were monitored for perinatal or neonatal mortality within 28 days after birth, for serious neonatal morbidity and for maternal mortality or serious morbidity within six weeks after delivery.
A total of 21 infants died, five of whom were excluded from all analyses because death was caused by congenital defects. Of the other 16 deaths, six were linked to difficult vaginal delivery, four to fetal heart-rate abnormalities during labor and six to a variety of other problems; these 16 infants were excluded from analyses of neonatal morbidity.
Overall, the risk of perinatal or neonatal mortality or serious neonatal morbidity was 67% lower in the planned cesarean section group than in the planned vaginal birth group. When these outcomes were examined in separate analyses, the risk of death during the perinatal or neonatal period was 77% lower among infants whose mothers had been randomized to the planned cesarean section group, and the risk of serious morbidity was 64% lower. No significant differences were found between the two groups in serious maternal morbidity or maternal mortality.
Thirteen of 14 subgroup analyses designed to assess the generalizability of the findings found no interactions between the women's characteristics and the planned method of delivery. However, the reduction in the risk of any perinatal or neonatal problem was much greater in countries that had a national perinatal mortality rate of no more than 20 deaths per 1,000 births than in those that had a perinatal mortality rate of more than 20 deaths per 1,000 (93% vs. 34%), as was the reduction in the risk of serious neonatal morbidity (92% vs. 8%).
The investigators point out that although this clinical trial was restricted to facilities with physicians skilled in vaginal breech delivery, the infants of women randomized to planned cesarean section were less likely to die or to experience poor neonatal outcomes than were those of women assigned to planned vaginal birth. A policy of planned cesarean section, they estimate, would save one baby from death or serious morbidity for every 14 additional cesarean sections performed; the number of additional cesareans needed to prevent one infant from having an adverse outcome could be as low as seven in countries with low perinatal mortality or as high as 39 in countries with high perinatal mortality. The researchers conclude that "a policy of planned vaginal birth is no longer to be encouraged for singleton fetuses in the breech presentation." --F. Althaus
1. Hannah ME et al., Planned caesarean section versus planned vaginal birth for breech presentation at term: a randomized multicentre trial, Lancet, 2000, 356(9239): 1375-1382.
*A fetus in breech presentation is positioned buttocks down rather than head down. In complete breech presentation, its hips and knees are flexed, but the feet are not below the fetal buttocks. In frank breech presentation, the hips are flexed and the knees extended.