Background: Nuchal translucency is widely used to screen for trisomy 21 in the first trimester of pregnancy. It has also been associated with other chromosomal abnormalities, genetic syndromes and congenital defects.
Objective: To evaluate the perinatal outcome of patients who showed nuchal translucency greater or equal to 95th percentile during the first trimester ultrasound screening, which underwent fetal karyotype.
Material and method: Case series. Fetuses with nuchal translucency greater or equal to 95th percentile were evaluated by fetal karyotype, second-trimester structural ultrasound scan, fetal echocardiography and postnatal clinical genetic evaluation, attended in the servicio de Genética of the Instituto Nacional de Perinatología Isidro Espinosa de los Reyes.
Results: 48 fetuses were evaluated. The karyotype was normal in 39 (81%) and abnormal in 9 (19%) cases of which three had trisomy 21, three monosomy X, two trisomy 18 and one 47,XYY In the cases with normal karyotype, 13 (33%) showed an abnormal second trimester ultrasound scan; among them, 12 had major congenital defects, 5 of them had abnormal cardiac findings that were confirmed by fetal echocardiography. In the group of 26 fetuses with normal karyotype and ultrasound, only 2 patients had minor birth defects.
Conclusions: Increased fetal nuchal translucency is frequently associated with chromosomal abnormalities and several congenital defects, mostly heart defects and genetic syndromes. Our findings are in accordance with other published reports where a complete follow-up of all patients with increased nuchal translucency is recommended even if they have a normal karyotype, due to the increased risk of having other congenital defects or syndromic entities.