Objective  To analyze effects of maternal socio-demographic factors and physical health during pregnant and puerperal period on birth defects of children and to provide evidences for early intervention of birth defects.

  Methods  We conducted a nested case-control study from 2013 through 2014 among pregnant women registered for prenantal healthcare and their children in Jiangbei district of Ningbo city, Zhejiang province. All the pregnant women giving births to infants with birth defects at the birth or diagnosed during the 2-year follow-up were recruited as the cases (n = 230); one control was matched to each of the cases by gender of the infant, the time of registry for prenantal healthcare (± one week), residing in a same residential district, hospitalized in medical institutions at same administrative level for the delivery. All the participants were followed up from 13-gestational week to 2-year after the delivery to collect relevant information. Paired t and chi-square test and binary logistic regression analysis were adopted in data analysis with SPSS 22.0.

  Results  Univariate analysis demonstrated that the cases had significantly higher ratios of nonlocal census register, low education, aged ≥ 30 years, infertility/spontaneous abortion and adnexal surgery history, assisted reproduction, and body mass index > 24 kg/m² at early pregnancy compared to the controls. Muntlivariate analysis revealed significantly increased risk of infants' birth defects for the pregnant women aged ≥ 30 years (odds ratio OR = 2.27), having threatened abortion (OR = 3.11), with pregnancy-induced hypertension (OR = 11.58), and with placental abnormality (OR = 2.78); while, with local census register was a protective factor against birth defects among the pregnant women.

  Conclusion   Monitoring on fetus development should be strengthened among the pregnant women aged 30 years and above and with various pregnancy-related abmormalities.