Prenatal diagnosis of sex chromosome abnormalities: the 8-year experience of a single medical center.

OBJECTIVE: To assess the indications for prenatal karyotyping of sex chromosomal abnormalities (SCAs) during pregnancy.

METHODS: All singleton pregnancies interrupted in our institute because of SCAs (1998-2005) were categorized into subgroups of 45,XO (Turner syndrome), 47,XXY (Klinefelter syndrome), 47,XXX and 47,XYY. The indications for prenatal diagnostic testing were recorded.

RESULTS: There were 67 SCAs pregnancies: 33% Turner syndrome, 28% Klinefelter syndrome, 21% 47,XXX and 18% 47,XYY. Maternal age was similar among the 4 groups (34 +/- 5, range 25-42 years). The main indications for fetal karyotyping were abnormal Down's syndrome (DS) screening or ultrasound findings, advanced maternal age (> or =35 years), and parental request. About 2/3 of the Turner and 47,XYY cases had either abnormal DS screening tests or sonographic findings, such as: increased nuchal translucency, mainly cystic hygroma and fetal hydrops. However, fetal karyotyping in more than 2/3 of the 47,XXX and 47,XXY cases was mainly performed because of advanced maternal age, and the diagnosis of fetal SCAs was coincidental (p <0.03).

CONCLUSIONS: Our recent suggestion to expand the DS screening capacity to other chromosomal abnormalities including SCAs is further supported. Prenatal detection seems to be promising for Turner syndrome and possibly for 47,XYY syndrome, while other SCAs are less likely to be detected either by ultrasound or biochemical screening.