五例单绒毛膜双羊膜囊双胎核型不一致的产前诊断

摘要

目的 探讨单绒毛膜双羊膜囊双胎核型不一致的形成机制及诊断方法.方法 对5例超声发现其中一胎正常、另一胎多发畸形的单绒毛膜双羊膜囊双胎行双羊膜腔穿刺,取双胎羊水行核型分析及16个多态性微卫星标记位点检测确定合子性质.结果 5例单绒毛膜双羊膜囊双胎中异常胎的染色体核型为3例45,X、1例47,XX,+9和1例47,XY,+18;其同胞正常胎的染色体核型均正常.多态性微卫星标记位点检测显示各对双胎16个位点完全一致,证实为单合子双胎.结论 单绒毛膜双羊膜囊双胎可能会出现核型不一致,后期延滞、染色体不分离和三体自救是导致单绒毛膜双羊膜囊双胎核型不一致的主要原因.双羊膜腔穿刺羊水行核型分析及合子性质鉴定是产前诊断单绒毛膜双羊膜囊双胎核型不一致的简单方法.对表型不一致的单绒毛膜双羊膜囊双胎有必要做双胎的核型分析和合子性质鉴定.%Objective To explore the mechanism and diagnostic method for monochorionic-diamniotic twins discordant for karyotype analysis.Methods Dual amniocentesis was performed on five pairs of monochorionic-diamniotic twins, which all consisted of a normal twin and one with multiple malformations revealed by ultrasound.Karyotype analysis was performed on amniocytes derived from each of the twins.Zygosity was also determined with DNA extracted from amniocytes with 16 polymorphic microsatellite markers.Results Three cases of 45 ,X, one case of 47 ,XX, +9 and one case of 47 ,XY, +18 were detected among the abnormal twins, while the normal fetuses all had a normal karyotype.DNA analysis suggested that, in all cases, the twins have shared the 16 polymorphic microsatellite markers, which confirmed their monozygosity.Conclusion Monochorionic-diamniotic twins may be discordant for karyotyping, for which anaphase lagging, chromosomal non-disjunction and trisomy rescue may be the underlying reasons.As a simple method, dual amniocentesis can be used to obtain amniotic fluid samples for karyotype analysis and determination of zygosity for such twins.