İncreased NT wıth normal karyotype

increased nuchal translucency marks not only the pregnancies complicated with chromosomal anomalies, but may also be found in fetuses with normal karyotypes. These pregnancies with increased NT and euploid karyotype may apparently be normal or candidate for certain structural or single gene defects. Nuchal edema (NT) may progress or undergo spontaneous resolution during the late first and early second trimester both in euploid and aneuploid pregnancies. According to recent sonographic observalions there is an a.ssociation between inereased NT and second trimester eystic hygroma, NT being the predecessor of the latter. This phenomenon provides basis for comparison of the natural history of simple hygroma in the first trimester and eystic hygroma in the second trimester of pregnaney. Pregnancies with inereased NT and normal karyotype have a high chance (more than 80%) of spontaneous resolution of the hygroma. Prenatal and neonatal progress has been reported uneventful in 89% of the cases, indicating a very good prognosis. However, cardiac and other structural malfrmations may occur in at least 20 per cent of the surviving embryos and more than 40 genetic syndromes have been reported up to now.
Second trimester fetal eystic hygroma, regardless of the underlying cause, carries a very poor prognosis and is correlated with unfavourable perinatal outcome. By contrast, increased NT may represent a similarly high risk of aneuploidy and an overall better prognosis in euploid cases. The improved prognosis for euploid fetuses with posterior hygroma detected in the first trimester may be related to the veıy early spontaneous resolution, since early resolution prevents irreversibile alterations.