Main findings
In this cohort that included 6264 Singaporean women, 25% of them increased their BMI category, while 5% of them lowered their BMI category between their first and second pregnancies. Approximately half of the women gained ≥1 kg/m2, of which one-third had excess gain of ≥3 kg/m2; only 10% lost >1 kg/m2 between pregnancies. Overall, BMI tended to change 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. Interpregnancy BMI gain was associated with increased risks of LGA, GDM and emergency caesarean delivery in the second pregnancy. Greater risks of these adverse outcomes were seen in women with excess interpregnancy BMI gain of ≥3 kg/m2. Conversely, an increased risk of low birthweight was observed in women with BMI loss between their first two pregnancies. The findings remained similar in sensitivity analyses restricted to women with BMI measured ≤12 weeks gestation for both pregnancies. When the results were further stratified by BMI in the first pregnancy (<23 or ≥23 kg/m2), a higher risk of emergency caesarean delivery was evident in women with a BMI <23 kg/m2 experiencing interpregnancy BMI gain, while higher risks of low birthweight and SGA were evident in women with a BMI ≥23 kg/m2 experiencing interpregnancy BMI loss. We believe that this is the first study to investigate the distribution and outcomes of interpregnancy weight change in Asian women between the first and second delivery.