ABSTRACT
<p><b>OBJECTIVE</b>To study the prevalence rates of birth defects in high and low risk areas in China.</p><p><b>METHODS</b>A population-based surveillance system on birth defects was used to obtain the prevalence rates of 24 kinds of major external birth defects from > or = 20 weeks of gestation to 7 days of life in selected areas in Shanxi and Jiangsu provinces.</p><p><b>RESULTS</b>The birth prevalence of birth defects (232.4 per 10,000 births) and neural tube defects (NTDs) (138.7 per 10,000 births) in four counties of Shanxi province were significantly higher than that in Taiyuan city (75.3 and 28.2 per 10,000 births, respectively). There was no significant difference for all selected birth defects between Wuxi city and Xishan counties in low risk areas. There was a 6.1-fold of higher prevalence for NTDs in Taiyuan city compared with that in Wuxi areas (4.6 per 10,000 births). In four counties of Shanxi province, the prevalence rates of anencephaly, spina bifida, hydrocephaly, cleft palate alone and polydactyly were significantly higher than in Wuxi areas. The NTDs prevalence rate in four counties of Shanxi was 30.2 times higher than in Wuxi areas. When compared with previous surveillance data, the NTDs prevalence rate did not present obvious declining trend in high risk areas. The birth prevalence rate had a 31.8% decrease when births were calculated after 28 gestational weeks and compared with those from 20 gestational weeks.</p><p><b>CONCLUSION</b>NTDs remained to be the most common birth defect seen in Shanxi province. The birth prevalence rate of NTDs in some areas of Shanxi province was among the highest that ever reported in the world in comparison with data from other countries and regions. The current prevalence rate in high risk areas in Shanxi province did not clearly show a declining trend. Programs on surveillance and prenatal diagnosis were proved to have made big impact on the rates of major external birth defects.</p>