Trisomy 18 in chorionic villus sampling: Problems and consequences

Abstract

Among 1547 patients undergoing first-trimester prenatal diagnosis, 100 fetal chromosome aberrations were detected. Thirteen of these involved chromosome 18. In two structural abnormalities of chromosome 18, the aberration could be excluded in amniotic fluid cells and two healthy infants were born. Trisomy 18 was not confirmed in amniotic fluid cells in three trisomy 18 mosaics. In eight non-mosaic trisomy 18 first-trimester diagnoses, the diagnosis was excluded by amniotic fluid cells or fetal cultures in four, and confirmed in the remaining four. Diagnosis of chromosome 18 aberrations in the direct preparation should be confirmed in the long-term culture of the chorionic villus sample or by amniotic fluid cultures.

Retrospective study of trisomy 18 in chorionic villi with fluorescent in situ hybridization on archival direct preparations

“…Confirmatory studies of long-term villus cultures have been proposed as a means of verification, as mesenchymal cells in the villus core are suggested to have a closer ontogenetic relation to the fetal cells than the trophoblast cells (Crane and Cheung, 1988). Our own results, as well as various earlier reports, argue against the use of long-term villus cultures (LTC) as the sole and sufficient independent confirmation (Wirtz et al, 1991;Miny et al, 1991;Ledbetter et al, 1992). Cytogenetic analysis of a subsequent amniotic fluid sample seems the most reliable procedure for verification of trisomy 18 in chorionic villi.…”

“…Trisomy 18 in non-mosaic, as well as mosaic, appearance in direct preparations of placental chorionic villi may not represent the chromosomal status of the fetus (Simoni et al, 1985;Wirtz et al, 1991). Confirmatory studies of long-term villus cultures are used as one of the means of verification.…”

Prenatal Detection of Two Different Monosomic Cell Lines by Chorionic Villus Sampling

“…Mosaicism is not a rare finding in CVS studies; when it is detected, serious problems in interpretation are raised (Wirtz et al, 1991;Simoni and Fraccaro, 1992;Fryberg et al, 1993). In the recently reported United Kingdom collaborative study of 7595 CVS cases, mosaicism was detected in 88 (1.16 per cent) and of these, only nine were confirmed in the fetus/liveborn while 53 were considered false positives (not confirmed on the fetus/ liveborn).…”

Cytogenetic diagnoses after chorionic villus sampling are less reliable in very‐high‐ or very‐low‐risk pregnancies

“…(1 990) experienced no false-negative diagnoses in 3000 cases; similarly Leschot et al (1990Leschot et al ( ) 0/1250Wirtz et al (1991) 0/1548; and the Canadian multicentre trial (Teshima et al, 1992) 011040. The U.S. collaborative study on CVS (Ledbetter et al, 1992) includes one false-negative prediction (i.e., case report by Martin et al (1986) in 11 473 direct preparations.…”