Impact of interpregnancy weight changes and perinatal outcomes: A retrospective study in Japan.

Previous studies have shown that interpregnancy weight fluctuations impact perinatal outcomes. In order to examine this in Japanese women, we analyzed the data of 2,861 women in their first and second pregnancies who delivered singletons between 2000 and 2022. We compared the second pregnancy perinatal outcomes of women whose interpregnancy body mass index (BMI) change was -1 to 1 unit with those of women whose BMI change was < -1 or ≥ 1 unit. An interpregnancy BMI change ≥ 1 unit was associated with an increased risk of developing gestational diabetes mellitus (adjusted odds ratio [aOR], 1.51; 95% confidence interval [CI], 1.18-1.95) and delivering a large for gestational age neonate (aOR, 1.67; 95% CI, 1.15-2.42) but a decreased risk of preterm birth (aOR, 0.66; 95% CI, 0.46-0.95). An interpregnancy BMI change < -1 unit was associated with a decreased risk of developing gestational diabetes mellitus (aOR, 0.51; 95% CI, 0.31-0.85). In a subgroup analysis of three groups divided according to prepregnancy BMI, interpregnancy BMI changes ≥ 1 unit in women with a BMI of < 18.5 kg/m2 before their first pregnancy were associated with a remarkable risk reduction of developing preterm birth (aOR, 0.30; 95% CI, 0.11-0.81). Interpregnancy BMI changes < -1 unit in women with a BMI of ≥ 25 kg/m2 before their first pregnancy were associated with a remarkable risk reduction of developing gestational diabetes mellitus (aOR, 0.33; 95% CI, 0.12-0.88). Weight gain during interpregnancy period was related to an increased risk of gestational diabetes mellitus and delivery of a large-for-gestational-age neonate, whereas weight loss was related to a decreased risk of developing gestational diabetes mellitus. These results indicate the importance of interpregnancy weight control as part of preconception care; therefore, women considering additional pregnancies should be educated on the importance of maintaining a healthy weight.