Background: Open neural tube defects are among the most common malformations of the fetus. Secondary prevention by early diagnosis during pregnancy and abortion of affected fetuses result in a marked reduction of NTD incidence at birth. The dramatic effect of folic acid for primary prevention of these defects led to recommendations for folic acid supplementation in women of reproductive age.

Objective: To describe the epidemiologic features of NTD in Israel in 1999±2000.

Methods: A national registry of NTD was begun in 1999. During the years 1999±2000, a non-syndromic NTD was diagnosed in at least 394 pregnancies (166 anencephaly, 166 spina bifida, 43 encephalo-cele, and 19 with other types of NTD). The religious-ethnic affiliation was known in 392 cases (209 Jews and 183 non-Jews).

Results: Despite a marked decline in the rate of NTD at birth in the last few decades, the total rates during pregnancy did not change significantly, demonstrating that the changes were secondary to termination of affected pregnancies. At birth, NTD were almost four times more frequent among non-Jews (3.6 per 10,000 live births for anencephaly and 5.9 for spina bifida) than among Jews (anencephaly 1/10,000 live births, spina bifida 1.4/10,000 live births). The complete data of the registry showed an approximately twofold difference in the overall rates during pregnancy between Jews (anencephaly 5.3, spina bifida 4.6, total 11/10,000 live births) and non-Jews (anencephaly 8.8, spina bifida 10.3, total 22.3/10,000 live births). The registry demon-strated that the significant differences in NTD incidence observed at birth between Jews and non-Jews are secondary to a combined effect of a higher frequency of the malformations among non-Jews and a lower proportion of termination of affected pregnancies among non-Jews.

Conclusions: The data presented here will serve as a basis for evaluating the impact of the Ministry of Health recommendations for folic acid supplementation on the incidence of NTD.