Data collection
The current analysis used the data set released in June 2016 (data set: jecs-ag-20160424). Specifically, we used three types of data: (1) M-T1, obtained from a self-reported questionnaire that was collected during the first trimester (the first questionnaire) and included questions regarding maternal medical background; (2) M-T2, obtained from a self-reported questionnaire that was collected during the second or third trimester (second questionnaire) and included questions regarding lifestyle and socioeconomic status; and (3) Dr-0m, collected from the medical records’ transcripts provided by each participant’s institution and that included obstetrical outcomes such as gestational age, birth weight, neonatal sex, and maternal body weight. The participants with singleton pregnancies after 22 weeks were included in the present study. The women with missing information were excluded from the analysis.