Data collection
The current analysis used data released in June 2016 (data set:
JECS-ag-20160424). Specifically, we used three types of data: (1) M-T1,
which are data on maternal medical background, obtained using a
self-reported questionnaire during the first trimester (the first
questionnaire); (2) M-T2, which are data on partner lifestyle and
socioeconomic status, obtained with a self-reported questionnaire during
the second or third trimester (second questionnaire); (3) Dr-0m, which
are data on obstetric outcomes such as gestational age and birth weight,
collected throughout pregnancy and extracted from participants’ medical
records transcripts (provided by relevant institutions).
Participants with singleton pregnancies after 22 weeks of gestation were
included in the present study. We excluded multiple pregnancies,
abortions, stillbirths, and deliveries with unknown gestational age.
Patients with uterine myomas were identified based on medical records
transcripts.