Mode of delivery and neonatal death in 17,587 infants presenting by the breech

To study the effects of caesarean section on neonatal mortality in infants presenting by the breech.

Population-based non-experimental comparison of infants presenting by the breech born vaginally with those born by caesarean section. Neonatal mortality rates were calculated for 250 g birthweight intervals. Weight-specific relative risks (RRs) were further adjusted for birthweight in 50 g categories.

New York City, 1978-1983. Data came from the Department of Health's computerized vital records on livebirths and infant deaths.

17,587 singleton breech livebirths greater than or equal to 500 g birthweight, with congenital anomaly deaths excluded. 6178 were born vaginally and 11409 were born by caesarean section.

Birthweight-specific and birthweight-adjusted neonatal mortality.

At birthweights of 501 to 1750 g, the risk of neonatal death for breech infants born vaginally was significantly higher than the risk for those born by caesarean section (weight-adjusted RR = 1.7). For breech infants with birthweights over 3000 g, the weight-adjusted risk was 5.6 times greater for a vaginal birth compared with caesarean section. The addition of 16 additional control variables in multiple logistic regression analyses did not change these RRs.

Population-based studies indicate that an increase in the caesarean section rate among breech singletons may be associated with increased neonatal survival, but a large multicentre randomized trial of management of breech presentation would answer the question much more definitively.