AIM: The effect of gestational weight gain on placental weight has not been elucidated. We aimed to examine the effect of body weight gain during pregnancy on the Japanese standardized z-score of placental weight, based on the pre-pregnancy body mass index. METHODS: This retrospective cohort study included Japanese women with singleton pregnancies who gave birth during 2013-2019 at Ohta Nishinouchi Hospital. Participants (n = 3610) were categorized by their pre-pregnancy body mass index: G1 (<18.5 kg/m2 ), G2 (18.5 to <20.0 kg/m2 ), G3 (20.0 to <23.0 kg/m2 ), G4 (23.0 to <25.0 kg/m2 ), and G5 (≥25.0 kg/m2 ). Multiple linear regression analysis was used to identify associations between insufficient or excessive gestational weight gain in each body mass index category and z-score of placental weight, with adjustments for maternal age, assisted reproductive technology, and maternal pre-pregnancy conditions, such as hypertension, diabetes mellitus, myoma uteri, and uterine anomalies. RESULTS: Among the 3610 women assessed, 479, 692, 1292, 435, and 711 were in G1-G5, respectively. In G1, G3, and G4, excessive weight gain increased the placental weight z-score ([B: 0.50, 95% confidence interval [CI]: 0.23-0.76], [B: 0.19, 95% CI: 0.19-0.33], and [B: 0.18, 95% CI: 0.10-0.26]). Insufficient weight gain decreased the placental weight z-score in G3 (B: -0.19, 95% CI: -0.33 to -0.06) and G4 (B: -0.21, 95% CI: -0.29 to -0.13) women. CONCLUSION: The effect of weight gain during pregnancy on placental size varies by pre-pregnancy body mass index. This result may guide personalized pre-conception counseling to improve the outcomes of offspring.
AIM: The effect of gestational weight gain on placental weight has not been elucidated. We aimed to examine the effect of body weight gain during pregnancy on the Japanese standardized z-score of placental weight, based on the pre-pregnancy body mass index. METHODS: This retrospective cohort study included Japanese women with singleton pregnancies who gave birth during 2013-2019 at Ohta Nishinouchi Hospital. Participants (n = 3610) were categorized by their pre-pregnancy body mass index: G1 (<18.5 kg/m2 ), G2 (18.5 to <20.0 kg/m2 ), G3 (20.0 to <23.0 kg/m2 ), G4 (23.0 to <25.0 kg/m2 ), and G5 (≥25.0 kg/m2 ). Multiple linear regression analysis was used to identify associations between insufficient or excessive gestational weight gain in each body mass index category and z-score of placental weight, with adjustments for maternal age, assisted reproductive technology, and maternal pre-pregnancy conditions, such as hypertension, diabetes mellitus, myoma uteri, and uterine anomalies. RESULTS: Among the 3610 women assessed, 479, 692, 1292, 435, and 711 were in G1-G5, respectively. In G1, G3, and G4, excessive weight gain increased the placental weight z-score ([B: 0.50, 95% confidence interval [CI]: 0.23-0.76], [B: 0.19, 95% CI: 0.19-0.33], and [B: 0.18, 95% CI: 0.10-0.26]). Insufficient weight gain decreased the placental weight z-score in G3 (B: -0.19, 95% CI: -0.33 to -0.06) and G4 (B: -0.21, 95% CI: -0.29 to -0.13) women. CONCLUSION: The effect of weight gain during pregnancy on placental size varies by pre-pregnancy body mass index. This result may guide personalized pre-conception counseling to improve the outcomes of offspring.