Common determinants of breech presentation at birth in singletons: a population-based study.

OBJECTIVE: To estimate common determinants of breech presentation at parturition.

STUDY DESIGN: A population-based cohort study (between 1/1/2001 and 31/12/2010) was conducted among all women who delivered a singleton baby in breech presentation from 22 completed weeks of gestation. A binary logistic regression was used to determine independent feto-maternal characteristics of breech presentation at birth, adjusted odds ratios and 95% confidence intervals. Variables were: gestational age, birth weight, maternal age, parity and gender of the baby, presence or absence of a history of cesarean section, gestational diabetes, gestational hypertension, pregnancy after assisted reproduction technology and congenital malformations.

RESULTS: From a population of 611,021 women; 28,059 were delivered in breech presentation (4.59%). Independent determinants of breech presentation at delivery were: gestational age and birth weight (the lower, the higher the incidence of breech at birth), parity (the frequency of breech decreased with increasing parity) and maternal age (the older the mother, the higher the odds for breech presentation). Women who had a scarred uterus, due to a previous cesarean section, women who gave birth to a female offspring and women whose baby showed a congenital malformation, were more prone to be delivered in breech presentation.

CONCLUSION: Low gestational age and birth weight, advanced maternal age, a scarred uterus, a female baby and a baby with a congenital malformation increased the odds for singleton breech presentation at parturition. The latter gradually decreased with increasing parity.