An increasing number of women are undergoing prenatal cytogenetic testing with amniocentesis or chorionic villous sampling on the basis of advanced maternal age, which is not a risk factor for TS. The results of such testing may be difficult to interpret in the context of predicting outcomes and counseling families. One Danish registry review found that of 83% of fetuses with suspected TS based on cytogenetic studies allowed to come to term, 80% resulted in live births with 30% of these having normal physical exam findings and normal karyotypes. [Gravholt: 1996] A recent study by a U.S. cytogenetic laboratory examined 74 cases of suspected 45,X karyotypes. Sixty-eight of these cases had 45, X karyotypes with fetal sonographic findings diagnostic of TS. Six of these cases had a 45, X karyotype with a normal fetal ultrasound. Of these 6, one was electively terminated, one was lost to follow-up, and four were live born. Of these 4, one had clinical features of TS and three were normal boys. [Huang: 2002] The available data thus suggests that prenatal cytogenetic diagnosis of TS should be accompanied by fetal ultrasonography. The likelihood of phenotypic TS is reduced if the results of fetal ultrasound show no characteristic TS features (e.g., no cystic hygroma, renal, or cardiac malformations). The use of prenatal cytogenetic testing alone has a relatively high false positive rate and should be interpreted cautiously when counselling families regarding outcome.
|Author:||Catherine Jolma, MD - 2/2010|
Huang B, Thangavelu M, Bhatt S, J Sandlin C, Wang S.
Prenatal diagnosis of 45,X and 45,X mosaicism: the need for thorough cytogenetic and clinical evaluations.
Prenat Diagn. 2002;22(2):105-10. PubMed abstract