Maternal Factors and Gestational Diabetes

Data on maternal age, ethnicity, education level, and self-reported pre-pregnancy weight were collected from the participants at recruitment. During a clinic visit at 26–28 weeks of gestation, maternal weight (SECA weighing scale model 803, SECA Corp., Hamburg, Germany) and height (SECA stadiometer model 213) were measured, and weight gain up to 26–28 weeks of gestation was derived by subtracting self-reported pre-pregnancy weight from the weight at 26–28 weeks. Pre-pregnancy BMI was calculated as reported pre-pregnancy weight divided by the mother’s measured height squared (kg/m²). At the same clinic visit, maternal cigarette smoking, alcohol drinking, and physical activities were assessed using a questionnaire while maternal blood was collected for analysis of plasma vitamin D and folate concentrations. Furthermore, oral glucose tolerance tests were administered and gestational diabetes mellitus (GDM) was defined based on the 1999 World Health Organization criteria [35 (link),36 (link)].