OBJECTIVEThis paper is to explore the relationships between the occurrence of structural birth defects and environmental risk factors on birth defects.

METHODSA survey was conducted by using a population-based case control study. A total number of 388 structural birth defects, which were detected after 28 weeks' gestational age to 7th day after birth in various hospitals were recruited in Wuxi from 2002 to 2004. The control group consisted of 1607 normal live births born in the same period. Multiple logistic regression model was used to analyze relationships between environmental risk factors and occurrence of structural birth defects after controlling women's education level and childbearing age.

RESULTSAmong those factors which affected birth defects, the exposure to toxic substances in working environment was the highest risk factor, with OR value as 5.37 (95 % CI : 3.60-7.99). Suffering from reproductive tract infections, high fever during first trimester gestation, and taking potential teratogenic drugs such as hypnotics and anti-convulsion drug agents, might significantly increase the risk of structural birth defects, with OR values (95% CI) as 3.38 (1.33-8.56), 3.57 (1.73-7.37) and 2.75 (1.57-4.83) respectively. However, the correlation between oral contraceptives intake within six months before pregnancy and risk of birth defects had no statistical significance. In addition, pollution of the residential environment, staying up all night and raising pets at home, had relatively lower association with birth defects, with OR values (95% CI) as 2.28 (1.75-2.98), 1.96 (1.21-3.18) and 2.50 (1.66-3.76) respectively, yet with a higher proportion of exposure to those factors in pregnant women. There was a significant increase in occurrence risks of birth defects with increase in the number of exposure to environmental risk factors. OR values for having one, two, three kinds of environmental risk factors were 1.60, 4.32 and 10.23 respectively.

CONCLUSIONThe common structural birth defects were affected by a number of environmental risk factors. There was also a dose-response relationship between the number of environmental risk factors and occurrence risks of structural birth defects noticed in our study.