Shaffer L G, Langlois S, McCaskill C, Main D M, Robinson W P, Barrett I J, Kalousek D K
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
Prenat Diagn. 1996 Oct;16(10):899-905. doi: 10.1002/(SICI)1097-0223(199610)16:10<899::AID-PD960>3.0.CO;2-M.
Karyotypically normal fetuses with completely trisomic or mosaic placentae may be at increased risk for intrauterine growth restriction (IUGR). Molecular and cytogenetic analyses on nine pregnancies with confined placental mosaicism (CPM) for trisomy 2 were performed at two collaborating centres. Seven cases were identified through prenatal testing of chorionic villi (CVS). Two of these seven cases demonstrated complete trisomy 2 while the remaining five cases showed various levels of trisomy 2 (33 per cent-75 per cent cells). Two cases identified after IUGR was observed in newborn infants demonstrated 65 per cent and 100 per cent trisomy 2 in cultured villi from term placentae. In all nine cases, blood chromosome analysis (n = 4), chromosome analysis of amniotic fluid cultures (n = 4), and cultured amnion (n = 5) were normal, failing to demonstrate any trisomic cells in tissues of fetal origin. Molecular studies on the fetal or newborn tissues using dinucleotide repeat polymorphisms on chromosome 2 revealed normal biparental inheritance of chromosome 2 in all nine cases. The parental origin studies of the extra chromosome 2 in the placenta showed that three cases were maternal in origin, at least two of which were consistent with a maternal meiotic non-disjunction giving rise to the trisomy 2, while in one case a paternal origin of the extra chromosome 2 was established.
核型正常但胎盘完全三体或嵌合三体的胎儿，发生宫内生长受限（IUGR）的风险可能会增加。在两个合作中心对9例21三体局限型胎盘嵌合（CPM）妊娠进行了分子和细胞遗传学分析。7例通过绒毛取样（CVS）产前检测确诊。这7例中有2例显示完全21三体，其余5例显示不同程度的21三体（细胞比例为33% - 75%）。在新生儿出现IUGR后确诊的2例中，足月胎盘绒毛培养显示21三体比例分别为65%和100%。在所有9例中，血液染色体分析（n = 4）、羊水细胞培养染色体分析（n = 4）以及羊膜培养（n = 5）均正常，未在胎儿来源组织中发现任何三体细胞。利用2号染色体上的二核苷酸重复多态性对胎儿或新生儿组织进行分子研究，结果显示所有9例中2号染色体均为正常双亲遗传。对胎盘中额外2号染色体的亲代来源研究表明，3例起源于母亲，其中至少2例符合母亲减数分裂不分离导致21三体，而在1例中确定额外的2号染色体起源于父亲。
