Association of pre-pregnant body mass index and gestational weight gain with timing of delivery

L. Puscasiu, H. Roman, R. Newman, T. F. Hulsey, T. C. Hulsey

Abstract: To evaluate the effect of both pre-pregnant body mass index and gestational weight gain on preterm delivery. Retrospective study using the pregnancy risk Assessment Monitoring System Phase IV data. Centers for Disease Control and Prevention and 22 state health departments. Women having delivered a live birth were randomly sampled using stratified systematic sampling. Women were asked to complete a self administered questionnaire, merged with the respective birth certificate. Those with multiple pregnancies, preterm premature rupture of fetal membranes, and those presenting with several indications for medically induced preterm birth were excluded. A multinomial logistic regression model and the Wald’s test were used to estimate and compare adjusted odds ratios associated with risk factors for preterm delivery and potential confounders. Main outcome measure. Gestational age at delivery.Results. The sample included 30,108 women representing a population of 1,495,474. The risk of very preterm birth (<33 WG) was significantly increased when compared to the risk of moderate preterm birth (33-37 WG) in women with either low or excessive weight gain, regardless of body mass index (BMI). Age <18 years, African American origin, Medicaid insurance, no prenatal care, smoking during pregnancy, or a large for gestational age fetus were associated with a significantly increased risk of very preterm birth compared to the risk of moderate preterm birth. Variations and interactions between the rates of prepregnant body mass index and weight gain during pregnancy impact preterm delivery. Their effects appear to be interactively related with the risk of preterm delivery and hence should not be studied separately.
Keywords: body mass index, weight gain, preterm delivery, pregnancy