EPIDEMIOLOGY OF NEURAL-TUBE DEFECTS

Epidemiologic studies have established clear variations in the occurre nce of neural tube defects (NTDs) associated with demographic and othe r factors. Methods of counting NTD-affected pregnancies and other birt h defects rely on multiple sources of information such as hospital rec ords and birth certificates. Widespread prenatal diagnosis of NTDs pre sents special challenges for birth defects monitoring programs. Even b efore prenatal diagnosis was possible, epidemiologists noted geographi c variation in NTD rates; distinctive recurrence patterns within famil ies; variations in NTD rates by race/ethnicity, socioeconomic strata, and sex of the infant or fetus; and changing rates over time. We revie w highlights of studies of these factors and some conclusions that can be drawn from NTD epidemiologic data. These conclusions include the i mportance of maternal diet, a finding that has led to preventive inter ventions, and the suggestion of multiple causes of NTDs, indicating th at no single prevention program may prevent the occurrence of all NTDs . We also discuss the relevance of epidemiologic data to NTD screening and counseling policies and the importance of prenatal diagnosis data . Future epidemiologic studies will need to incorporate prenatal recor ds, particularly to study trends. Other emerging themes in epidemiolog ic research include collaboration between different birth defects moni toring programs, new information from unique geographic areas, new tec hniques to study gene-environment interactions, and a multidisciplinar y emphasis on measuring the effectiveness of prevention programs. Publ ished 1998 Wiley-Liss, Inc.dagger.