Aims: Patient Information: About one-third of embryos with Nuchal Thickening (NT) have chromosomal abnormalities. One of these abnormalities is Klinefelter syndrome (47XXY). The aim of this case report was to indicate the importance of prenatal diagnosis with consideration of anomalies reports in both screenings of the first and second trimester of pregnancy as well as the importance of NT and the need for further chromosomal studies in these conditions.
A 29-year-old woman with the first pregnancy was referred to Screening Clinic of Sarem Hospital for the first stage of aneuploidy screening in gestational age of 13 weeks and 2 days. The screening results of the first trimester were normal and in the second screening, the Quad marker testing (four tests of Inhibin A, Free β-hCG, AFP, and UE3) was conducted in gestational age of 16 weeks; the risk of Fetal Neural Tube Defects  and Down syndrome were reported again in the low-risk range. Amniocentesis was asked for the patient for a definitive diagnosis because of the high NT range. In the review and analysis of amniotic fluid cells, karyotype was reported as 47XXY (Klinefelter syndrome).
Conclusion: In aneuploidy screening, only estimating the risk of common trisomies of 13, 18, and 21 is not the case. NT amount must be examined separately. The prenatal diagnosis of these disorders is effective in planning and future prognosis of pregnancy. Klinefelter syndrome is one of those chromosomal abnormalities, which occurs as a XXY karyotype with an outbreak of 1 in 10,000 in boys, and, unfortunately, it is not diagnosed until the puberty after manifesting itself as a demonstration of hypogonadism. Early diagnosis and alternative hormone therapy can make natural maturation process in these cases.