Pregnancy outcomes of normal karyotype fetuses with increased nuchal translucency

Background: 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.Methods: 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.Results: 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.Conclusion: 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.