They point out that women with a prior cesarean delivery are at higher risk for malpresentation in future pregnancies – and they speculate that in many such cases a breech infant might have been the reason for c-section.
Dr. Jane B. Ford and colleagues at the University of Sydney analyzed cross-sectional and longitudinally linked birth, hospital and birth defect data sets to determine breech presentation risks and recurrence rates. Their findings appear in the May issue of BJOG: An International Journal of Obstetrics and Gynaecology.
The study included 113,854 women with two births and 21,690 with three, between 1994 and 2002 in New South Wales. The births were all singletons delivered after 37 or more weeks of gestation.
Overall, the rate of breech presentations per 100 births was 4.2 in a first pregnancy, 2.5 in a second pregnancy, and 2.2 in a third.
However, after one breech delivery, the recurrence rate in a second pregnancy was 9.9% (relative risk 4.4). For women with two breech pregnancies, the risk for recurrence in a third was a whopping 27.5% (RR 13.9).
Fourteen percent of breech-presenting babies in first pregnancies were born vaginally. This increased to 23% when the first breech was in a second pregnancy, and to 54% if a second breech followed a vaginal delivery. But if a first breech delivery was by cesarean section, a c-section was used again in 99% of second breeches.
Placenta previa in a first or second pregnancy and/or birth defect in a second pregnancy were the greatest risk factors for malpresentation recurrence, the authors report. Other factors included birth weight relative to gestational age, maternal age, and maternal diabetes.
Dr. Ford and her team advise, “The increased risk of a recurrent breech presentation…may justify ultrasound monitoring for identification of subsequent breech presentation for term pregnancies where there is a history of a breech-presenting infant.”