Distribution of interpregnancy BMI change
Figure 1 shows the cross-sectional trends of BMI change over
the interpregnancy interval by weight status at 12 weeks of gestation in
the first pregnancy. Overall, BMI tended to change (increase or
decrease) among women who had the second delivery in the first two years
after the first, and was stable at that level among women who delivered
later, regardless of the initial weight status. Figure 2A shows
the comparisons of interpregnancy BMI change and weight status at 12
weeks gestation in the first pregnancy. Women who were overweight and
obese in their first pregnancy tended to have interpregnancy BMI loss or
gain as compared to those who were underweight and normal weight, who
tended to be BMI stable (p<0.001).
In total, 24.5% of women gained weight between pregnancies and
progressed to a higher BMI category; while 5.4% of women lost weight
and dropped to a lower BMI category. Although at least 90% of women who
were overweight or obese in the first pregnancy remained at least
overweight in the second pregnancy, nearly two-thirds of women with
normal weight and half of women who were underweight remained in the
same weight status in the first and second pregnancies (Figure
2B ). Similar distributions of interpregnancy BMI change status and
weight status in the second pregnancy were observed across weight status
in the first pregnancy based on the WHO conventional cut-offs(Table S2) .