Some aspects of the epidemiology of human minor birth defects and morphological variants in a completely ascertained newborn population (Madison study).

In 4319 infants examined at birth who were without major birth defects those with a "remarkable" pregnancy outcome, i.e., low birth weight (less than 2500 g), long gestation (greater than or equal to 43 weeks), stillborn, or twin status, were more likely to have a minor birth defect than the remainder. With regard to the 2 most frequent defects, simian crease and folded helix, the increase in the former was of about the same order (1.6-2.1 -fold) in those with remarkable outcome of all types, but the increase in the latter was particularly great in twins (approximately 3.1-fold) compared with the other remarkable outcomes (approximately 1.3-fold). With regard to variants, which were defined as those features scored that occurred in 4% or more of the newborn population, some (flat and small hemangioma on face and scalp, Brushfield spots, flat nasal bridge, hyperflexed thumbs, hydrocele, and mild calcaneovalgus) exhibited a trend towards negative association with low birth weight and a trend to positive association (with exception of hemangioma and calcaneovalgus) with long gestation, suggesting they may simply be indirect markers of gestational age. There was a trend to a slight decrease in the frequency of minor defects with increasing maternal age, similar to the trend for major defects.