Phenotypic heterogeneity in neural tube defects: a clue to causal heterogeneity.

We report here retrospective data on 991 liveborn and stillborn infants with neural tube defects (NTDs) born to Utah residents from January 1, 1940 to December 31, 1979. Data were obtained from multiple sources including approximately 1.25 million vital statistics records and several hundred physician and hospital charts. Causal heterogeneity among NTD patients is presumed because 6% of our cases have other congenital anomalies not part of the NTD field defect. A significant association of NTDs with oral clefts is noted. Sex ratios and empiric recurrence risks for isolated NTDs and NTDs associated with other major malformations are also calculated.