[Possible factors associated with postpartum weight changes and weight retention]

Objectives　Focusing on maternal weight change from pre-pregnancy to 18 months postpartum, this study aimed to explore the possible factors associated with postpartum weight retention to provide obesity prevention strategies for women.Methods　A cross-sectional survey was conducted from July to November 2021. Data were obtained from 543 mothers who attended health checkups for 18-month-old infants in 16 Aomori Prefecture municipalities using self-administered questionnaires. Study components included basic maternal characteristics and information on infants at birth and mothers after childbirth. Postpartum weight retention was defined as weight retention <2 kg at 18 months postpartum. Comparative analysis of maternal weight and body mass index (BMI) between the retention and non-retention groups was performed using the Mann-Whitney U test. Factors associated with postpartum weight retention were examined using the χ² test, Fisher's exact test, and logistic regression analysis.Results　Maternal weight retention distribution at 18 months postpartum was 132 (59.5%) in the retention group and 90 (40.5%) in the non-retention group. Statistically significant differences between groups were observed for age (P < 0.05), employment status (P < 0.05), weight gain against pre-pregnancy BMI (P < 0.05), current breastfeeding status (P < 0.05), and BMI at 18 months postpartum (P < 0.01). Logistic regression analysis with weight retention as the dependent variable showed that unemployment (odds ratio [OR]: 3.76, 95% confidence interval [Cl]: 1.41-10.07), weight gain exceeding recommendations (OR: 3.31, 95% Cl: 1.39-7.90), current breastfeeding (OR: 3.32, 95% Cl: 1.34-8.20), and obesity at 18 months postpartum (OR: 6.06, 95% Cl: 2.49-14.73) were associated with non-retention. No association was observed with health guidance on weight management at municipalities or medical institutions.Conclusion　This study revealed that employment status, weight gain during pregnancy, current breastfeeding status, and BMI at 18 months postpartum were possible determinants of maternal postpartum weight retention. These findings suggest that regular maternal weight monitoring beyond postnatal checkups and providing support according to living and childcare environments are necessary.