The effects of preconception examinations on birth defects: a population-based cohort study in Dongguan City, China.

Objective: To evaluate the effect of preconception examinations programs on the prevention of birth defects in Dongguan City during 2013-2017. Methods: The data were from preconception examinations system and the birth defects surveillance system during 2013-2017. The study population included 63,175 infants born to mothers accepted preconception examinations during pregnancy (the screening group) and 649,862 infants whose mother did not check (the control group). The infants included for stillbirth, dead fetus, live birth between 28 weeks of gestation and 7 days after birth and legal pregnancy termination. The risk ratios (RRs) and 95% confidence intervals (CIs) were calculated to examine for the association between birth defects and preconception examinations. We also conducted a stratified analysis based on infant gender and disease classification, and maternal age and region. Results: The incidence of birth defects in the screening group was 134.55/10,000, while that in the control group was 241.53/10,000. Preconception examinations can effectively reduce the incidence of birth defects (BDs) (RR: 0.557, 95%CI: 0.520-0.597). Bifid spine (RR: 0.076, 95%CI: 0.011-0.545), anencephalia (RR: 0.134, 95%CI: 0.033-0.543) and anorectal atresia or stenosis (RR: 0.151, 95%CI: 0.048-0.471) were controlled best, and Down syndrome (RR: 0.684, 95%CI: 0.435-1.075) was no effect. Young maternal age (14-19 years) and old maternal age will increase the risk of birth defects. Preconception examinations had the best effect for pregnant women under 25 years of age (RR: 0.465, 95%CI: 0.387-0.559), and were relatively poor for women aged 30-34 years (RR: 0.678, 95%CI: 0.593-0.776). The incidence of the urban was significantly higher than that of the rural. The effect of preconception examinations to prevent birth defects was more effective in urban areas (RR: 0.453, 95%CI: 0.391-0.525) than in rural areas (RR: 0.577, 95%CI: 0.533-0.625). The incidence of BDs in males was higher than that in females. Conclusions: By implementing preconception examinations project, birth defects in Dongguan have been well controlled. This can provide reference for other developing countries to prevent birth defects.