Pregnancy outcomes of normal karyotype fetuses with increased nuchal translucency

Although the association between first-trimester increased nuchal translucency (NT) and chromosomal defects is well-defined, there is little knowledge about the importance of increased NT in fetuses with normal karyotypes. Hence, this study was designed to evaluate outcomes of normal karyotype fetuses with increased NT.

This observational retrospective study was conducted on 720 pregnancies with increased NT (>3mm) at 11 to 13 weeks of gestational age in Yas Hospital, Tehran, Iran, from 2016 to 2020. Study outcomes were incidence of preeclampsia, intrauterine growth restriction) IUGR (, preterm labor, fetal anomaly, cardiac malformations, hydrops fetalis, abortion, and intrauterine fetal death (IUFD) in pregnancies without evident chromosomal karyotype abnormalities.

Out of 720 participants who underwent karyotyping in the study center, 523 fetuses had normal karyotype results. In the pregnancies assessed for outcome, 357 (68.3%) reached live birth, 104 (19.9%) aborted, and 62 (11.9%) resulted in IUFD.
Study outcomes including preeclampsia (<0.001), IUGR (<0.001), preterm labor (<0.001), fetal anomaly (<0.001), cardiac malformations (<0.001), hydrops fetalis (0.017), abortion (<0.001), and IUFD (<0.001) resulted in a statistically significant difference in the distribution of cases across NT intervals.

This study demonstrated adverse pregnancy outcomes increased with increasing NT despite normal karyotyping. Hence, tight observation of mothers and fetuses should be done in normal karyotype fetuses with increased NT.