Male-to-female gender ratio in fetuses with increased nuchal translucency

Objective: To describe gender distribution in fetuses with increased nuchal translucency (NT) measurements. Methods: All fetuses with mild (2.5-2.9 mm) and moderate (3.0-3.5 mm) NT enlargement at 12.0-12.6 weeks gestation were studied. The Z test for proportions was used to compare the gender distribution of this study group to that of all babies born at Roosevelt Hospital in 2008, and to compare the gender distributions of the subgroups. Results: 5109 patients received screening at 12.0-12.6 weeks gestation. 44 fetuses had mild and 28 had moderate enlargement, with a male-to-female ratio of 3.8:1.0, much higher than the 1.06:1.0 ratio among total births at Roosevelt Hospital in 2008 (p < 0.0001). Male-to-female ratio was 7.8:1.0 in fetuses with mild and 1.8:1.0 with moderate NT enlargement (p = 0.03). Among fetuses with mild NT enlargement, 3 males had aneuploidy; among those with moderate enlargement, 6 fetuses had aneuploidy, 3 males and 3 females. Seven pregnancies with aneuploidy were voluntarily terminated. All pregnancies carried to term were healthy. Conclusions: More males than females had mild NT enlargement on first-trimester screening, but unless aneuploidy was detected they had normal birth outcomes. A slightly larger NT may be normal in males, while indicating possible fetal abnormalities in females.