Participants
We recruited reproductive-age women who participated in National Free
Preconception Health Examination Project (NFPHEP) from January 2015 to
September 2017 in Dongguan of Guangdong province of China. The details
of the NFPHEP were described elsewhere (25). Briefly, women intended
pregnancy within six months, were provided with free preconception
examinations by well-trained health workers, including a standardized
questionnaire and laboratory examinations. Then, the subsequent
pregnancy outcomes of women (number of fetus, infant outcome,
birthweight, gestation, date of delivery, etc.) were follow-up from
medical records. Basic information included demographic characteristics
(maternal age, nation, levels of education, height, weight, BMI, etc.),
lifestyle (history of passive smoking, work condition of exposure to
radiation/heat/organic solvent/heavy metal/ pesticides/other toxic
substances etc.), history of choric disease (diabetes, hypertension,
thyroid disease, heart disease, anemia), reproductive history
(spontaneous/induced abortion, stillbirth, pregnancy, parity, etc.). In
strict accordance with National Guide to Clinical Laboratory Procedures,
serum FPG level of women was detected by glucose oxidase or hexokinase
methods in the local laboratories, and accepted the external quality
assessment and quality control biannually (26).
This study was approved by the Ethical Committee of Maternal and
Children Health Care Hospital of Donguan City. The informed consents
were obtained from each participant.