Trisomy 7 in chorionic villi: Follow‐up studies of pregnancy, normal child, and placental clonal anomalies

Abstract

Cytogenetic study of chorionic villi sampled because of advanced maternal age revealed, after overnight culture, an apparently non-mosaic trisomy 7. Amniocentesis showed exclusively normal mitoses, and the pregnancy continued normally. One hundred mitoses from cord blood of the normal newborn revealed a non-mosaic 46,XX complement. No cells with a proven trisomy 7 were found in cultures from either of two biopsies of the morphologically normal placenta, but the peripheral biopsy showed in multiple cultures an abnormal clone: 47,XX, +20, -2, -21, +t(2;21)(p13;q22). To our knowledge, this is the first case of non-mosaic trisomy 7 detected on CVS which has had follow-up studies of amniotic fluid, cord blood, and term placenta.

Resorbed co‐twin as an explanation for discrepant chorionic villus results: Non‐mosaic 47,XX, +16 in villi (direct and culture) with normal (46,XX) amniotic fluid and neonatal blood

“…Maternal age in our case was 38 years, with trisomy 16 being strongly maternal age-dependent (Morton er al., 1988). The same hypothesispersistence of villi from a deceased co-twin--could explain other reports of nonmosaic trisomy 16, 18, and 20 in villi, yet normal complements in cultured fetal fibroblasts (Mikkelsen, 1985;Simoni et al, 1985;Hogge et al, 1986); trisomy 7 detected in villi associated with normal karyotype in fetal skin (Bartels et al, 1986); and trisomy 7 present in villi despite normal amniotic fluid cells and a normal neonatal blood complement (DeLozier-Blanchet et al, 1988). A rare instance of trisomy 16 associated with confined chorionic mosaicism has also been reported in a liveborn infant with multiple anomalies (Watson et al, 1988).…”

The significance of trisomy 7 mosaicism in chorionic villus cultures

“…Hsu and Perlis (1984) cite a case with 46/47,+7 mosaicism following amniocentesis and a normal cord blood fetal karyotype. Previous reports of mosaic trisomy 7 following CVS have the abnormal cell line either in direct analysis or in cultured cells, or in both, but never in the fetus (Callen et al, 1988;Leschot et al, 1087;McKinley et a!., 1988;Tibiletti et al, 1986;Blanchet et al, 1988;Bartels et al, 1086). Follow-up studies and details of the reported trisomy 7 findings are summarized in Table 1 along with the two present cases.…”

Intrauterine growth retardation associated with chromosomal aneuploidy confined to the placenta. Three observations: Triple trisomy 6,21,22; trisomy 16; and trisomy 18

“…As most trisomies result in early embryological/fetal demise, they are rarely found in third-trimester fetuses or neonates. Confined placental mosaicism (CPM) appears to be an exception that is tolerable for the fetus even with 'exotic' or 'non-viable' trisomies: e.g., trisomy 3 (Guerneri et izl., 1989;Schulze et al, 1987), trisomy 7 (Elartels et al, 1986Delozier-Blanchet et al, 1988;McKinley et al, 1988), trisomy l;! (Kalousek et al, 1987), trisomy 15 (Schulze et al, 1987), trisomy 16 (Hashish et al, 1989;Williams et al, 1989), and trisomy 22 (Stioui et al, 1989).…”