Body mass index change between pregnancies and small for gestational age births.

Abstract

To estimate whether maternal weight changes between pregnancies influence the risk for small for gestational age (SGA) births. SGA cases (n = 8,062) below the tenth percentile birth weight for gestational age were selected from liveborn singletons born of Missouri residents during 1989-1997. Normal weight controls (n = 8,062) were selected according to birth year. The risk of SGA from interpregnancy body mass index (BMI) change and other maternal factors was estimated using logistic regression analysis. An increase in BMI between pregnancies decreased SGA risk (adjusted odds ratio = 0.8; 95% confidence interval 0.7, 1.0). Other risk factors were prior SGA (4.4; 4.0, 4.8), preeclampsia/eclampsia (2.6; 2.1, 3.2), maternal cardiac disease (1.8; 1.1, 2.9), inadequate weight gain (1.9; 1.8, 2.2), and cigarette smoking (1.9; 1.7, 2.3 for 1-9 cigarettes per day; 2.5; 2.2, 2.8 for 10-19/d; and 2.8; 2.5, 3.3 for 20/d or more). Increase in interpregnancy BMI lowers SGA risk, but adequate weight gain during pregnancy is more effective.