Study Protocol for the Japan Pregnancy, Eating, Activity, Cohort (J-PEACH) Study: Investigating Perinatal Maternal Lifestyle and Infant Health.

The prevalence of low-birth-weight infants has increased over the past 40 years to approximately 9-10% of Japanese live births. This study aims to identify healthy lifestyle behaviors and psychosocial factors contributing to appropriate perinatal outcomes, gestational weight gain, and postpartum weight change. The Japan Pregnancy, Eating, Activity, and Cohort study was initiated in 2020 in Tokyo, Yamagata/Miyagi, Osaka, and Fukuoka. Participants will be enrolled at approximately 12 weeks of gestation, with follow-up at 18-27 and 35-41 weeks of gestation and 1, 6, and 12 months postpartum. Approximately 3000 participants are targeted: Yamagata/Miyagi (n = 300), Tokyo (n = 1500), Osaka (n = 800), and Fukuoka (n = 400). Participants will complete questionnaires on healthy lifestyle behaviors (dietary intake, physical activity, and circadian rhythm), psychosocial factors, weight control, and behavioral intentions. Medical records will be reviewed for antenatal checkup data. The primary outcomes will include gestational weight gain, infant birth weight, perinatal complications, breastfeeding, and postpartum weight change. Demographic and psychosocial factors and lifestyle behaviors will be examined as covariates and potential confounders. Biological samples will be collected in Tokyo and Yamagata. The study's findings will inform efforts to improve perinatal care guidelines through evidence-based recommendations.