The role of cesarean delivery of infants in breech presentation remains controversial. Lee and colleagues analyzed birth data for the years 1989, 1990 and 1991, published by the National Center for Health Statistics, to compare neonatal mortality among infants with breech presentation who were delivered vaginally and by cesarean.
The authors examined data on 371,692 singleton live births of infants with breech presentation whose birth weight and method of delivery were known. Infants weighing less than 500 g (1 lb, 2 oz) at birth were excluded. The births included in the study were categorized into four delivery groups: primary cesarean section, repeat cesarean section, vaginal delivery and vaginal delivery after cesarean section. The overall rate of cesarean delivery in the study population was 85.5 percent.
The predominant mode of delivery varied with the weight of the infant. Vaginal delivery, including vaginal birth after cesarean section, was the method of delivery in 55.4 percent of the infants with birth weights under 749 g (1 lb, 10 oz). In contrast, cesarean section was the mode of delivery in 86.3 percent of the infants who weighed over 2,500 g (5 lb, 8 oz).
In each category of birth weight, the neonatal mortality rate was much lower in the infants delivered by cesarean section than in those delivered vaginally. The differences in mortality rates were most marked in the first hour of life, ranging from a nearly threefold difference in infants weighing 2,000 to 2,499 g (4 lb, 6 oz to 5 lb, 7 oz) to a nearly 13-fold difference in infants weighing 2,500 g or more.
The observed differences in the mortality rate could not be explained by congenital malformations or other causes of mortality. After statistical adjustments were made for the variations in birth weight, a 3.8-fold higher risk of death in the first day was demonstrated in the infants delivered vaginally compared with the risk in infants delivered by primary cesarean section. For up to 28 days after birth, the weight-adjusted risk of neonatal mortality for infants with breech presentation was 2.6-fold greater for the vaginal delivery group than for the cesarean delivery group.
The authors also identified the limitations of their study, including the shortcomings of using data from linked birth and death certificates and the limited availability of information about other factors that could have influenced the choice of delivery mode. They mention that the increased mortality rate associated with vaginal births could reflect a lack of experience in vaginal breech delivery among American physicians. In spite of these concerns, the authors conclude that infants with breech presentation delivered by cesarean section had lower birth weight–specific neonatal mortality compared with vaginal deliveries.