Contribution of changing risk factors to the trend in breech presentation at term.

BACKGROUND: Recent population-wide changes in perinatal risk factors may affect rates of breech presentation at birth, and have implications for the provision of breech services and training in breech management.

AIMS: To investigate whether changes in maternal and pregnancy characteristics explain the observed trend in breech presentation at term.

MATERIALS AND METHODS: All singleton term (≥37 week) births in New South Wales during 2002-2012 were identified through birth and associated hospital records. Annual rates of breech presentation were determined. Logistic regression modelling was used to predict expected rates of breech presentation and these were compared with observed rates over time. A priori predictors included maternal age, country of birth, parity, smoking during pregnancy, diabetes, pregnancy hypertension, placenta praevia, previous singleton term breech, previous caesarean section, infant sex, gestational age, birthweight and congenital anomalies. Hospital and Medicare data were used to assess concomitant trends in external cephalic version.

RESULTS: Among 914 147 singleton term births, 3.1% were breech at delivery. Rates of breech presentation declined from 3.6% in 2002 to 2.7% in 2012 (test for trend P < 0.001), but was predicted to increase from 3.6% in 2002 to 4.3% in 2012 because of increased maternal age, nulliparity, maternal diabetes, history of breech presentation and previous caesarean section. However, use of external cephalic version appears to have increased over time.

CONCLUSIONS: Breech presentation at delivery has decreased in New South Wales. Increased use of external cephalic version likely accounts for this decline, as changes in risk factors do not.