Gestational diabetes mellitus, pre-pregnancy body mass index and gestational weight gain predicts fetal growth and neonatal outcomes.

Background: Gestational diabetes mellitus (GDM), body mass index (BMI) and gestational weight gain (GWG) are salient predictors of pregnancy-outcomes. However, findings on the association between GDM, BMI, and GWG with fetal growth measures are limited.

Objective: The aim of this study was to investigate the effect of GDM on fetal growth measures and birth outcomes.

Methods: All participants came from Tongji Maternal and Child health cohort, in which pregnant women were enrolled before 16 weeks of gestation and had their weights measured regularly during antenatal visits. GDM was diagnosed by oral glucose tolerance test (OGTT) during 24-28 weeks of gestation. Ultrasound measurements of fetal bi-parietal diameters (BPD), head circumferences (HC), abdominal circumferences (AC) and femur length (FL) before birth were collected and neonate outcomes were obtained from the hospital records. Odds ratios were calculated using logistic regression to assess the association of GDM, pre-pregnancy BMI, and GWG with fetal growth measures of ultrasound and birth outcomes, while controlling confounding.

Results: Of 3253 singleton pregnant women, 293 (9.0%) were diagnosed with GDM, 357 (11.0%) were overweight before pregnancy, and 1995 (61.3%) had excessive GWG. GDM was associated with decreased intrauterine fetal growth measurements including BPD and AC. Maternal pre-pregnancy overweight was associated with increased fetal HC and neonatal birth weight and length, women gained excessive GWG had increased fetal growth measurements of BPD, HC, AC, FL, neonatal birth weight and length. Offspring of GDM women had increased odds of cesarean section 1.31 (1.03, 1.66) and preterm birth 2.02 (1.05, 3.91) in unadjusted models, but these associations disappeared after adjustment. Compared with neonate born to mothers with normal pre-pregnancy weight, those born to underweight mother had higher risk of SGA, and lower risk of cesarean section, LGA and macrosamia, whereas those born to overweight mother had increased risk of cesarean section, LGA and macrosamia. Compared with neonate born to mothers of adequate GWG, neonate of women with excessive GWG had elevated risk of cesarean section, LGA and macrosamia, but lower risk of preterm birth and SGA.

Conclusion: Pre-pregnancy BMI, GWG and GDM all associated with fetal growth and birth outcomes. The effect of GDM decreased after adjusting pre-pregnancy BMI and GWG. Early screening and management of GDM, preventing excessive GWG could help protect fetuses of GDM mothers from adverse birth outcomes.