Effects of maternal pre-pregnancy overweight on macrosomia in women with gestational diabetes mellitus

Abstract

Objective To explore the relationship between maternal pre-pregnancy body mass index (BMI) and neonatal birth weight in women with gestational diabetes mellitus (GDM). Methods From the pregnant women who received prenatal care and delivered at the Department of Obstetrics and Gynecology of Peking University First Hospital between May 1, 2012 and November 1, 2013, 550 GDM women aged 20-49 years and with single gestation were enrolled in this study. According to the pre-pregnancy BMI, the GDM women were divided into overweight group (BMI ≥24.0, n=145) and non-overweight group (BMI<24.0, n=405). Gestational weight gain, glucose level of 75 g oral glucose tolerance test, glucose control, delivery mode and neonatal birth weight were compared between the two groups. The influencing factors for macrosomia and the relationship between maternal pre-pregnancy BMI and neonatal birth weight were analyzed. Independent sample t-test, Chi-square test, multivariate Logistic regression and Pearson correlation analysis were used for statistical analysis. Receiver operating characteristic (ROC) curve was used to determine the optimal threshold of pre-pregnancy BMI to predict macrosomia. Results Compared with the data of non-overweight group, fasting glucose level [(5.1±0.5) vs (5.3±0.5) mmol/L, t=-4.599], 1 h glucose level [(9.4±1.7) vs (9.8±1.6) mmol/L, t=-2.742], proportion of poor glucose control [20.5% (83/405) vs 33.1% (48/145), χ2=8.281], proportion of cesarean delivery [37.8% (153/405) vs 55.2% (80/145), χ2=13.160], neonatal birth weight [(3 306±424) vs (3 476±545) g, t=-3.374], and ratio of macrosomia [5.4% (22/405) vs 16.6% (24/145), χ2=16.291] were all higher in overweight group (all P<0.01). The mean gestational weight gain per week in overweight group was significantly lower than in non-overweight group [(336±123) vs (402±131) g, t=5.136, P<0.01]. Pre-pregnancy overweight (OR=4.009, 95%CI: 2.039-7.881), gestational weight gain per week (OR=1.003, 95%CI: 1.001-1.005) and fasting glucose level (OR=2.285, 95%CI: 1.326-3.938) were the influencing factors for macrosomia (all P<0.01). Pre-pregnancy BMI of GDM women was positively related with neonatal birth weight (r=0.179, P<0.01). Pre-pregnancy BMI ≥22.8 was defined as the optimal threshold to predict macrosomia (ROC area under curve=0.691). Conclusions Maternal pre-pregnancy overweight is a significant risk factor for macrosomia in women with GDM. GDM women with pre-pregnancy overweight should control glucose level and weight gain during pregnancy in order to reduce the risk of macrosomia. Key words: Diabetes, gestational; Body mass index; Obesity; Weight gain; Fetal macrosomia