Congenital malformations in Utah.

The rate of malformed children in Utah of 11.7 per 1,000 liver births, derived from 128,857 birth certificates, ws not high compared with other non-Utah studies. Rates of selected malformations also were not high. The rate of malformed children varied by county of residence. San Juan County reported the highest percentage of mothers receiving late or infrequent prenatal care, the lowest mean level of public education, and the highest rate of malformed children in the state. The rate was not significantly associated with the large population of Indians residing in that county since by controlling for residence, the variation by race was eliminated. The overall rate was positively associated with maternal age rimarily due to an increased frequency of Down's syndrome. The impact of the "maternal age effect" on the state malformation rate, however, was not large. By controlling for maternal age, the slight association between increased rate of malformed children and increasing birth order was eliminated. The rate of malformed children was higher for parents having a low level of education, infrequent prenatal care, or who were not married. There was also a strong negative association of birth weight with the rate of malformation. Analysis of rates of selected malformations suggested that the low birth weight was a sequela to intrauterine growth retardation caused by severe congenital malformation. The validity and etiologic implications of these results await further investigation.