Holoprosencephaly associated with caudal dysgenesis: a clinical-epidemiological analysis.

We have studied 9 cases with the combination of some form of holoprosencephaly and any degree of caudal dysgenesis. The cases were identified through the Spanish Collaborative Study of Congenital Malformations (ECEMC). Of the 9 cases, 6 infants had an aneuploidy syndrome, one had Meckel syndrome, and 2 cases were of unknown etiology. We determined that the prevalence figure for the association of both conditions in the same child was 0.08 per 10,000 livebirths, and 18.8 times higher for stillbirths (i.e., 1.50/10,000). This prevalence is significantly higher than what would be expected by chance.