Information was obtained from the same questionnaire (23 risk factors listed) of cases and controls. We used a multivariate logistic model, which described variables significantly increased risk of birth defects. The risk factors included maternal educational levels, medicine taken during pregnancy and antenatal care. It was suggested to strengthen antenatal care was the main preventive measure against birth defects. Information was obtained from the same questionnaire (23 risk factors listed) of cases and controls. We used a multivariate logistic model, which described variables significantly increased risk of birth defects. The risk factors included maternal educational levels, medicine took during pregnancy and antenatal care. It was suggested to improve antenatal care was the main preventive measure against birth defects.