Impact of changes in recommendation of optimal gestational weight gain in Japan: A retrospective study in a single tertiary center

Aim: In March 2021, the Japanese Ministry of Health, Labour and Welfare revised the optimal gestational weight gain standards. In this study, we examined whether this revision affected gestational weight gain and low birth weight rates. Methods: We analyzed the records of singleton pregnant women who underwent checkups from their 1st trimester and delivered at our institute after 37 weeks between 2020 and 2021 (before the revision) and between 2022 and 2023 (after the revision). Pregnancy outcomes were assessed in the following four groups stratified by pre-pregnancy body mass index (BMI): underweight (BMI: <18.5 kg/m(2)), normal-weight (BMI: 18.5-24.9 kg/m(2)), overweight (BMI: 25-29.9 kg/m(2)), and obese (BMI: >= 30 kg/m(2)). Leaflets on the optimal gestational weight gain standards for each group were distributed to all pregnant women at the first prenatal checkup. Results: In each group, gestational weight gain did not change before and after the revision, with the corresponding values of 10.8 kg and 11.1 kg in the underweight (p = 0.94), 10.7 kg and 10.4 kg in the normal weight (p = 0.14), 9.7 kg and 9.2 kg in the overweight (p = 0.32), and 7.4 kg and 6.7 kg in the obese (p = 0.44) groups. Furthermore, the prevalence of low birth weight did not decrease in all groups. Conclusions: No significant differences in gestational weight gain or low birth weight were observed after the revision of the 2021 gestational weight gain recommendations. Merely distributing leaflets to pregnant women may not be sufficient to improve gestational weight gain or reduce low birth weight rates.