Maternal obesity, gestational hypertension, and preterm delivery.

Objective: To study maternal obesity as a risk factor for preterm delivery.

Methods: Maine State Birth Records Database from 1996 through 2006 was evaluated to investigate obese pregnant women compared with normal weight women regarding risk for preterm delivery. Multiple risk factors and outcomes were studied in univariable and multivariable models.

Results: Among 58,112 pregnant women, 8% (n = 4653) gave birth to preterm infants. Univariable analyses revealed a relationship between obesity and increased risk of prematurity. In multivariable regressions, the most important intermediate variable appears to be gestational hypertension/preeclampsia.

Conclusions: As maternal body mass index increases in pregnancy, the risk of preterm delivery and other maternal complications increases. The obesity-prematurity relationship is complex, with hypertensive disorders of pregnancy playing a crucial role. More detailed analyses of causal pathways are warranted.