Genetic counseling for trisomy X syndrome diagnosed by amniocentesis: a case report

[Introduction] Trisomy X is a sex chromosome abnormality that occurs in approximately 1 in 1,000 female births. We provided genetic counseling to a pregnant woman and her husband following the prenatal diagnosis of trisomy X by amniocentesis. [Case] A 27-year-old pregnant woman, gravida 2, para 1, underwent a prenatal checkup by her general practitioner. Nuchal translucency (NT) of 3.4 mm was detected in the fetus at 11 weeks of gestation and had disappeared by 12 weeks of gestation. The pregnant woman and her husband consulted our unit for genetic counseling at 13 weeks of gestation. Although we did not detect any NT or other abnormality in the fetus, the parents were concerned about possible abnormalities and requested amniocentesis. Amniocentesis followed by chromosomal analysis at 16 weeks of gestation revealed a 47, XXX karyotype. We explained the results and characteristics of trisomy X to the couple. The frequency of trisomy X is 1 in 1,000, and it can be characterized by tall stature, developmental delay, learning disability, anxiety, and mood disorders. However, the features of trisomy X vary and we were therefore unable to predict the newborn's precise postnatal physical and psychological characteristics. The couple decided to continue the pregnancy, and a female newborn was delivered at 38 weeks of gestation weighing 2,418 g. The karyotype was confirmed as 47,XXX, but her development to date (age of 2 years) has been normal. [Conclusions] Careful genetic counseling is important for pregnant women and their partners following a prenatal diagnosis of trisomy X