Impact of change of maternal body mass index between pregnancies on the risk of recurrent term low birth weight

Abstract

ON THE RISK OF RECURRENT TERM LOW BIRTH WEIGHT LAURA LAFFINEUSE (F), AMY GOODWIN, MARC COLLIN, BRIAN MERCER, CASE-MetroHealth Medical Center, Reproductive Biology, Maternal-Fetal Medicine, Cleveland, Ohio, CASE-MetroHealth Medical Center, Pediatrics, Cleveland, Ohio OBJECTIVE: The purpose of this study was to evaluate the relationship between pre-pregnancy maternal body mass index (mBMI) and the risk of subsequent low birth weight (LBW) at term. STUDY DESIGN: This is an analysis of data from a single institution from 1996 to 2004. Data was collected by chart review at the time of discharge and maintained in an electronic database. We included only those who delivered their 1st and 2nd pregnancies at our institution, and delivered a term singleton infant in both pregnancies. Pre-pregnancy mBMI’s were calculated for the 1st and 2nd deliveries. We evaluated the impact of mBMI on birth weight (BWT) and LBW (BWT ! 2500 grams). The impact of LBW in the 1st pregnancy on the rate of subsequent LBW was also assessed. We also evaluated change in mBMI between pregnancies to determine if weight gain or oss altered the risk of subsequent LBW. A p!0.05 was considered significant. RESULTS: 1,029 women met our inclusion criteria. We found a positive correlation between BWT in the 1st and 2nd pregnancies (p! 0.0001, R=0.24). Increasing mBMI was associated with increasing BWT (p!0.0001) in the first pregnancy. Women delivering a LBW infant in the 1st pregnancy were more likely to have LBW in the 2nd pregnancy (14.3 vs. 3.9%, relative risk 3.7, p = 0.02). Overall the risk of LBW in the 2nd pregnancy did not change with increasing or decreasing mBMI between pregnancies (p = 0.17). After controlling for LBW in the 1st pregnancy (p = 0.005), and pregravid mBMI (p = 0.06), risk of LBW in the 2nd pregnancy was not altered by change in mBMI (ANOVA, p = 0.36). CONCLUSION: Though LBW at term is associated with low mBMI and a prior LBW delivery, change in mBMI between pregnancies does not alter this risk.