Assessment of covariates and outcome definition
Pre-pregnancy body mass index (BMI) was calculated by dividing
self-reported pre-pregnancy weight (kg) by height squared
(m2). According to the International Association of
Diabetes and Pregnancy Study Groups (IADPSG) criteria26, gestational diabetes mellitus (GDM) was diagnosed
when OGTT fasting ≥ 5.1 mmol/L or OGTT 1 hour ≥ 10.0 mmol/L or OGTT 2
hour ≥ 8.5mmol/L. The date of last menstrual period was used to estimate
gestational age (in weeks). PTB was defined as gestational week less
than 37 weeks.