The association of gestational diabetes mellitus with fetal birth weight.

AIMS: Gestational diabetes mellitus (GDM) and different time-point glucose levels might have different effects on fetal birth weight. The aim of this study was to further evaluate the associations of GDM and different time-point blood glucose levels with fetal birth weight in a prospective cohort study.

METHODS: This prospective cohort study was conducted in Zhoushan Maternal and Child Health Hospital, Zhejiang, from August 2011 to May 2015. 1232 pairs of singleton, full-term newborns and their mothers without other pregnant and perinatal complications were selected as participants.

RESULTS: Of the 1232 women, 234 had GDM. GDM was positively associated with birth weight (β = 99.5 g, P = 0.0002), gestational age-specific Z-score of birth weight (β = 0.23, P = 0.0003), and an increased risk of large for gestational age (LGA; OR = 1.79, 95%CI: 1.11-2.89) and macrosomia (OR = 2.13, 95%CI: 1.34-3.40). Compared with abnormal fasting plasma glucose (FPG) during the second trimester, abnormal postload glucose in oral glucose tolerance test had significantly higher birth weight and gestational age-specific Z-score of birth weight, and an increased risk of macrosomia. Abnormal FPG and abnormal postload glucose had significantly joint effect on birth weight (β = 161.4 g, P = 0.0192), gestational age-specific Z-score of birth weight (β = 0.42, P = 0.0121) and risk of macrosomia (OR = 3.24, 95%CI: 1.21-8.67) and LGA (OR = 5.73, 95%CI: 2.20-14.90). Compared with abnormal blood glucose during the first trimester, GDM had significantly higher birth weight and gestational age-specific Z-score of birth weight. Abnormal blood glucose during the first trimester and GDM had significantly joint effect on birth weight (β = 125.8 g, P = 0.0010), gestational age-specific Z-score of birth weight (β = 0.30, P = 0.0013) and risk of macrosomia (OR = 2.34, 95%CI: 1.28-4.30) and LGA (OR = 2.53, 95%CI: 1.37-4.67). However, we did not find blood glucose during the first trimester independently associated with birth weight.

CONCLUSIONS: GDM was significantly associated with higher birth weight and an increased risk of LGA and macrosomia. Fetal growth was mostly influenced by postload glucose levels, rather than FBG. Moreover, different time-point blood glucose levels had significantly joint effects on birth weight and risk of LGA and macrosomia.