The relation between small size for gestational age and the sex ratio of children with birth defects

Abstract

Background: Infants with birth defects are more likely to be born small for gestational age (SGA) than are other infants. This study describes a relation noted between the percentage SGA and the percentage male among children with various defect types. The data source was case records collected by the Metropolitan Atlanta Congenital Defects Program, a population-based, active surveillance system, during 1968 through 1998.

Methods: The study calculated the correlation between the percentage male and the percentage SGA for isolated cases of 44 different defect types for male-dominant and female-dominant defects separately.

Results: The correlation coefficient was -0.47 (P < 0.01) for male-dominant defects and 0.20 (P > 0.05) for female-dominant defects. Male-dominant defects were more likely to show less than 15% SGA and more likely to show the strongest risk differences by sex.

Conclusions: These results are consistent with genetic causation of strongly skewed sex ratios, at least among male-dominant defects. Review of the literature suggests that defects with sex ratios closer to 1 are likely to have lower recurrence risks and therefore are less likely to be inherited than are other defects with skewed sex ratios. Sex ratios closer to 1 and a high percentage SGA may be markers of acquired or environmental birth defects.