GSTM1 and type 2 diabetes mellitus: Then 5800 pregnant women were excluded, including Hb < 110 g/L in the first trimester (n = 100), SF ≥ 30 μg/L in the first trimester (n = 5134), other special types of anemia (n = 189), history of chronic hypertension (n = 35), type 1/type 2 diabetes (n = 58), and pregnancy complicated with heart disease (n = 6), duration of residence in Kunming < 1 year (n = 22), twin and multiple pregnancy (n = 128).