Categories of Pre-pregnancy BMI
Pre-pregnancy BMI was calculated by dividing the weight in kilogram (kg)
by the square of the height in meters (m), and was classified into four
categories based on Chinese criteria12: underweight
(BMI <18.5kg/m2), normal weight
(18.5-23.9kg/m2), overweight
(24.0-27.9kg/m2), and obesity
(≥28.0kg/m2).