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Counselling implications of chromosomal abnormalities other than trisomy 21 detected through a maternal serum
E Sheridan1, J Williams, A Caine
1St Jame's Hospital, Leeds, UK.
Objective:
To identify counselling requirements, we reviewed the frequency and type of non-trisomy 21 chromosome abnormalities found at amniocentesis after maternal serum screening for Down's syndrome.
Design:
The study involved a review of the cytogenetic results of amniocenteses performed because of a raised maternal serum screening risk.
Setting:
The maternal serum screening and amniocenteses were performed at hospitals in the Yorkshire region.
Sample:
1715 amniocenteses were performed as a result of a raised maternal serum screening risk for the period 1990 to 1993.
Methods:
The cytogenetic results were classified into the main categories of numerical and structural chromosomal abnormalities.
Main Outcome Measures:
The nature and frequency of abnormal cytogenetic results were identified in which parental samples were required in order to determine if the abnormal finding was de novo or familial and/or for which specialist genetic counselling was required.
Results:
Sixty-nine pregnancies of 1715 amniocenteses were identified with a chromosomal abnormality (4.0%): 35 (2.0%) with trisomy 21 and 34 (2.0%) with another chromosomal abnormality. For 20 of these 34 abnormalities, parental karyotypes were required and in 29 of the 34 specialist genetic counselling was required.
Conclusions:
Women undergoing maternal serum screening and, in particular, those proceeding to amniocentesis, should be informed that there is an equal chance that a chromosomal abnormality other than trisomy 21 will be found at amniocentesis, the nature of which usually requires parental samples and specialist counselling.