Lipid measurement
Fasting blood samples were collected at gestational week 6–8, 16, 24 and 36, and non-fasting blood samples were collected at 42 days postpartum. Serum TG, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and glucose levels were measured by the Hitachi type 7180 automatic biochemical analyzer (Hitachi High-Tech Science Systems Corporation, Yokohama, Japan) at the laboratory of Fuxing Hospital affiliated to Capital Medical University.