Male gender as a favorable prognostic factor in pregnancies with enlarged nuchal translucency

Objective: The aim of this study was to investigate the influence of fetal gender on pregnancy outcome in fetuses with enlarged nuchal translucency (NT). Methods: Pregnancy outcomes of all women who underwent an NT measurement at our institution between January 2000 and November 2007 were retrospectively reviewed. Separate analyses were performed for fetuses with normal and with enlarged (≥=95th percentile) NT. Results: A normal NT was measured in 3637 males (51.4%) and 3435 females (48.6%). Of the fetuses with enlarged NT 365 were males (57.4%) and 271 females (42.6%) (P = 0.001). In this group a normal pregnancy outcome - of those pregnancies for which the outcome was known - was registered for 187/332 (56.3%) of the male fetuses and 98/249 (39.4%) of the female fetuses (P < 0.001; relative risk (RR) for adverse outcome for male gender, 0.72). Eighty percent of the chromosomally normal male fetuses with an enlarged NT had an uneventful pregnancy outcome; this increased to 90% when only the male fetuses with NT measurements ≥95th percentile and <99th percentile and normal karyotype were considered (RR for adverse outcome for male gender, 0.47). Conclusion In a population of fetuses with enlarged NT there are significantly more males. Male fetuses with enlarged NT and normal chromosomes have an almost two-fold greater chance of a favorable outcome than females. We believe that a minimal degree of NT enlargement in male fetuses without genetic or structural anomalies may be interpreted as a feature of accelerated growth or, alternatively, as a maturational delay of the cardiovascular system more common in males, leading to moderately increased nuchal fluid accumulation. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.