A population-based case-control study of risk factors for breech presentation.

Objective: We evaluated relationships between breech presentation and infant, maternal, and pregnancy characteristics of singleton births.
Study Design: A population-based case-control study (3588 breech cases, 8183 controls) was conducted with data from the 1987 to 1988 Washington State birth certificate.
Results: Low birth weight, short gestational age, primiparity, and older maternal age were associated with increased risk of breech birth, and after we controlled for these factors, the following were also associated with breech birth: hydrocephalus, established maternal diabetes, congenital malformation of the infant, smoking during pregnancy, and late or no prenatal care. In addition, black and Filipino women had decreased risk of breech presentation compared with white women.
Conclusion: Several different maternal and infant characteristics appear to increase risk of breech birth, suggesting that there may be several different biologic mechanisms leading to breech presentation.