45,X 46,XY MOSAICISM - THE ROLE OF ULTRASOUND IN PRENATAL-DIAGNOSIS AND COUNSELING/

The purpose of this study was to assess the benefit of ultrasound eval uation for fetuses with prenatally diagnosed 45,X/46,XY mosaicism. The charts of all patients who underwent chorionic villus sampling and/or amniocentesis between 1 March 1990 and 31 October 1995 were screened for 45,X/46,XY mosaicism. Cases were divided on the basis of the resul ts of the confirmatory amniocentesis into two groups: (1) confined pla cental mosaicism (n = 4); and (2) true fetal 45,X/46,XY mosaicism (n = 4). All patients underwent high-resolution detailed ultrasound study between 16 and 22 weeks. If the initial ultrasound study failed to vis ualize fetal genitalia, scanning was repeated in 2 weeks. Chromosome a nalysis was carried out on the newborn's skin to confirm the prenatal result. Six cases were found to have 45,X/46,XY mosaicism on chorionic villus sampling. Amniocentesis indicated a normal 46,XY male karyotyp e for three fetuses and true fetal follow-up amniocentesis. At birth, this newborn was documented to have normal male genitalia and a 46,XY karyotype. An additional two cases underwent amniocentesis only and we re documented to have 45,X/46,XY mosaicism. High-resolution detailed u ltrasound study between genitalia and one fetus with ambiguous genital is. Of the four neonates with true 45,X/46,XY mosaicism this was the o nly one found to have ambiguous genitalia. Of the four neonates with t rue 45,X/46,XY mosaicism this was the only one found to have ambiguous genitalia. We conclude that the work-up of patients with 45,X/46,XY m osaicism should include ultrasound study to look for ambiguous genital ia. This allows appropriate counselling regarding the natural history of the condition and aids in the planning for management in the postna tal period.