Empiric recurrence risk for neural tube defects (NTD) in Krakow region

A sample of 347 families in the Krakow region of Southern Poland with at least one child with anencephaly and/or myelomeningocele or encephalomeningocele were ascertained by multiple selection. The birth prevalence of neural tube defects in this population was 75/80, 584 (0.93/1000). The risk of affected individuals among the probands' sibs was 3.3% (+/- 1.6), about 38 times the population prevalence at birth. The empiric risk was higher for female than for male sibs of the proband. Also, the probability of occurrence was higher for sibs of male probands. The differences were nonsignificant. The heritability calculated on the regression of siblings on propositi was 76% (+/- 7).