Obesity as a potential risk factor for stillbirth: The Japan Environment and Children's Study

Satoshi Shinohara; Ryoji Shinohara; Reiji Kojima; Sayaka Horiuchi; Sanae Otawa; Megumi Kushima; Kunio Miyake; Hideki Yui; Tadao Ooka; Yuka Akiyama; Hiroshi Yokomichi; Zentaro Yamagata; Japan Environment and Children's Study Group

doi:10.1016/j.pmedr.2023.102391

Obesity as a potential risk factor for stillbirth: The Japan Environment and Children's Study

Prev Med Rep. 2023 Aug 28:35:102391. doi: 10.1016/j.pmedr.2023.102391. eCollection 2023 Oct.

Affiliations

¹ Department of Obstetrics and Gynecology, Yamanashi Prefectural Central Hospital, 1-1-1 Fujimi, Kofu, Yamanashi 400-8506, Japan.
² Center for Birth Cohort Studies, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan.
³ Department of Health Sciences, School of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, Japan.
⁴ Department of Epidemiology and Environmental Medicine, School of Medicine, University of Yamanashi, Chuo, Japan.

Abstract

The relationship between high body mass index (BMI) >25 kg/m² and risk for stillbirth in the Japanese population remains unclear. This study aimed to estimate the impact of maternal obesity on the risk of stillbirth in a Japanese population. This prospective cohort study used data from the Japan Environment and Children's Study, which recruited pregnant individuals between 2011 and 2014. A total of 93,772 fetuses were considered eligible for inclusion in this study. Stillbirth (fetal death before or during labor at ≥22 completed weeks of gestation) rates were compared among four pre-pregnancy BMI groups: underweight (<18.5 kg/m²), reference (18.5 to <25.0 kg/m²), overweight (25.0 to <30.0 kg/m²), and obese (≥30.0 kg/m²). The association between pre-pregnancy BMI and the risk of stillbirth was estimated using multiple logistic regression analyses. The overall stillbirth incidence was 0.33% (305/93,722). Compared with the reference group, the risk of stillbirth was significantly higher in the overweight group (adjusted odds ratio [aOR]: 1.55; 95% confidence interval [CI]: 1.08-2.23) and the obese group (aOR: 2.60; 95% CI: 1.59-4.24). The overall incidence of early stillbirth (i.e., <28 weeks) was 0.17% (155/93,722). Similarly, after adjusting for potential confounding factors, the risk of early stillbirth was significantly higher in the obese group (aOR: 4.33; 95% CI: 2.44-7.70). Increased maternal BMI was associated with an increased risk of stillbirth in the Japanese population. Therefore, counselling women planning for pregnancy on the importance of an appropriate pre-pregnancy BMI to minimize the risk of stillbirth is important.

Keywords: Japanese; Maternal body mass index; Obesity; Overweight; Stillbirth; Women.