Implications
Our findings have important clinical and public health implications.
Abnormal pre-pregnancy BMI is common among reproductive age women around
the world. Evidence of management of women with different weight in
pregnancy were mainly from west countries where have high prevalence of
overweight and obesity (including severe obesity) and have different BMI
classification from China,6 and which may not adopt to
other developing countries like China. Our findings from more than
660000 women confirmed that compared with women with normal weight, a
statistically significant increase in risk estimate by 6% of PTB, 23%
of SGA in underweight women; 17% of LGA, 18% of primary caesarean
delivery, and 44% of stillbirth in overweight women; and 12% of PTB,
32% of LGA, and 45% of primary caesarean delivery in obese women. This
suggested that clinical evidence-based recommendation and counselling
for management of BMI before and during pregnancy among reproductive age
women might be necessary for reducing the risk of adverse pregnancy
outcomes in China. The finding also suggested the recommendation and
counselling should tailor to maternal age, as the association of
pre-pregnancy BMI with adverse pregnancy differed according to maternal
age.