Methods
In the present study, we investigated the data of the Japan Environment
and Children’s Study (JECS), which is a nationwide, government-funded,
birth cohort study10 that was started in January 2011
to investigate the effects of environmental factors on children’s
health. The eligibility criteria for the JECS participants (expectant
mothers) were as follows: (1) residing in one of the study areas at the
time of recruitment and expected to reside continually in Japan for the
foreseeable future, (2) an expected delivery date between August 01,
2011 and mid-2014, and (3) the ability to participate in the study
without difficulty (i.e., the participant needed to be able to
comprehend the Japanese language and complete the self-administered
questionnaires). This study was conducted in 15 Regional centers across
Japan as described previously.10 The JECS protocol was
reviewed and approved by the Ministry of the Environment’s Institutional
Review Board on Epidemiological Studies and by the ethics committees of
all participating institutions. The JECS was conducted in accordance
with the principles of Declaration of Helsinki and other nationally
valid regulations and guidelines. Written informed consent was obtained
from all participating women. There was no patient and public
involvement in this study.