Threatened abortion Daily passive tobacco smoke Anemia Nutritional status and Dietary habits Cereal grains consumption Hypertension Potato consumption Other pregnancy complications Meat consumption Mental state during pregnancy Animal giblets consumption Medicine use during pregnancy Antibiotics Egg

Objective: To explore the periconceptional factors affecting the risk of neural tube defects (NTDs), we carried out a hospital-based case-control study in China. Methods: A 1:1 matched case-control study was conducted. With self-designed questionnaires, we solicited relevant information from 459 case mothers and 459 control mothers selected in two provinces of China through face-to-face interviews. Univariate and multivariate conditional logistic regression analyses were conducted to evaluate the effect values by odds ratios (ORs) and 95% confidence intervals (95%CIs) with SAS9.1.3.software. Results: Daily passive tobacco smoke exposure was a risk factor for total NTDs (OR1⁄4 8.688, 95%CI1⁄4 2.329–32.404). Diet adjustment in the first trimester (OR1⁄4 0.061, 95%CI1⁄4 0.014–0.274), periconceptional folic acid intake (OR1⁄4 0.059, 95%CI1⁄4 0.011–0.321) and health education (OR1⁄4 0.251, 95%CI1⁄4 0.081–0.781) were protective factors for total NTDs. Differences in factors and their effects on NTDs were found for the three subtypes of NTDs: anencephaly, spina bifida and encephalocele. Conclusions: Daily passive tobacco smoke exposure, diet adjustment in the first trimester, periconceptional folic acid intake and health education were associated with NTDs.