Background: Infants with birth defects are more likely to be born small for
gestational age (SGA) than are other infants. This study describes a relat
ion noted between the percentage SGA and the percentage male among children
with various defect types. The data source was case records collected by t
he Metropolitan Atlanta Congenital Defects Program, a population-based, act
ive surveillance system, during 1968 through 1998.
Methods: The study calculated the correlation between the percentage male a
nd the percentage SGA for isolated cases of 44 different defect types for m
ale-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 def
ects 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 strongl
y skewed sex ratios, at least among male-dominant defects. Review of the li
terature Suggests that defects with sex ratios closer to 1 are likely to ha
ve lower recurrence risks and therefore are less likely to be inherited tha
n are other defects with skewed sex ratios. Sex ratios closer to 1 and a hi
gh percentage SGA may be markers of acquired or environmental birth defects
. Teratology 63:52-56, 2001. Published 2001 Wiley-Liss, Inc.(dagger)