A comparison of risk factors for breech presentation in preterm and term labor: a nationwide, population-based case-control study.

PURPOSE: To determine if the common risks for breech presentation at term labor are also eligible in preterm labor.

METHODS: A Finnish cross-sectional study included 737,788 singleton births (24-42 gestational weeks) during 2004-2014. A multivariable logistic regression analysis was used to calculate the risks of breech presentation.

RESULTS: The incidence of breech presentation at delivery decreased from 23.5% in pregnancy weeks 24-27 to 2.5% in term pregnancies. In gestational weeks 24-27, preterm premature rupture of membranes was associated with breech presentation. In 28-31 gestational weeks, breech presentation was associated with maternal pre-eclampsia/hypertension, preterm premature rupture of membranes, and fetal birth weight below the tenth percentile. In gestational weeks 32-36, the risks were advanced maternal age, nulliparity, previous cesarean section, preterm premature rupture of membranes, oligohydramnios, birth weight below the tenth percentile, female sex, and congenital anomaly. In term pregnancies, breech presentation was associated with advanced maternal age, nulliparity, maternal hypothyroidism, pre-gestational diabetes, placenta praevia, premature rupture of membranes, oligohydramnios, congenital anomaly, female sex, and birth weight below the tenth percentile.

CONCLUSION: Breech presentation in preterm labor is associated with obstetric risk factors compared to cephalic presentation. These risks decrease linearly with the gestational age. In moderate to late preterm delivery, breech presentation is a high-risk state and some obstetric risk factors are yet visible in early preterm delivery. Breech presentation in extremely preterm deliveries has, with the exception of preterm premature rupture of membranes, similar clinical risk profiles as in cephalic presentation.