Association of pre-pregnant body mass index and gestational weight gain with the timing of delivery and fetal growth in singletons

Abstract

The aim of the study was to evaluate the effect of both pre-pregnant body mass index (BMI) and weight gain during pregnancy on fetal growth. The Pregnancy Risk Assessment Monitoring System (PRAMS - Phase IV) data (2000-2001) was used for analysis. The primary outcome was fetal growth, defined by small for gestational age (SGA) and large for gestational age (LGA). A multinomial logistic regression model and the Wald’s test were used to estimate and compare odds ratios associated with risk factors and confounders. The sample included 58,709 women, representing a population of 2,303,387. As compared to normal weight women with adequate weight gain, the risk of an SGA newborn was significantly increased in underweight women with low weight gain, and significantly lower in normal weight, overweight and obese women with excessive weight gain. LGA risk was significantly lower in under-, normal- and overweight women with low weight gain and increased in all women with excessive weight gain as well as in obese women with normal weight gain. The risk of LGA was also increased in women aged over 35 years, for those reporting an unintended pregnancy, no prenatal care or presenting with diabetes mellitus. Variations and interactions between maternal pre -pregnant BMI and weight gain appear to be closely intertwined, highlighting the importance of studying the two factors together rather than separately. <br/><a href=