Natural history of trisomy 21 fetuses with increased nuchal translucency thickness

Increased fetal nuchal translucency thickness at 10-14 weeks of gestation can identify 80% of trisomy 21 pregnancies. However, a potential disadvantage of screening in the first trimester of pregnancy is that earlier screening preferentially identifies those chromosomally abnormal pregnancies that are destined to miscarry. In this study, we report on the outcome of six fetuses with increased nuchal translucency thickness and trisomy 21 whose parents chose to continue with the pregnancy. During the second trimester, the nuchal translucency resolved in five of the cases and in one it evolved into nuchal edema. Therefore, resolution of translucency with advancing gestation is not indicative of a normal karyotype. All pregnancies resulted in live births, suggesting that increased nuchal translucency does not necessarily identify those trisomic fetuses that are destined to die in utero.