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The study analyzed maternal groups by prepregnancy BMI: 900 underweight (<18.5), 5517 normal (18.5-23.9), 2068 overweight (24.0-27.9),and 890 obese (>28). Mean age and parity rose slightly with BMI, from 27.5 ± 4.2 years and 1.2 ± 0.5 in the underweight group to around 29-29.7 years and 1.4 ± 0.6 in the obese group. Birthweight (2426-2514 g) and body length (46.9-47.2 cm) were similar across groups. higher education proportions decreased from 56.9% (normal) to 38.4% (obese). Over 95% of each group were Han Chinese, and urban registration increased from 80% (underweight) to 89% (obese). Employment rates were 60-65%, with smoking rates <1%. Anemia incidence dropped with higher BMI from 64.1 to 40.3%, while diabetes and hypertension rates rose, from 16.3 to 33.9% for diabetes, and 3.2-23.1% for hypertension.
