染色体平衡易位与优生研究

为研究染色体平衡易位与优生的关系，应用外周血、羊水、精液作染色体制备与显带，并进行遗传咨询、产前诊断和跟踪随访。对3727例外周血染色体检查发现41个平衡易位家系（31个相互易位，10个罗伯逊易位）和56例平衡易位携带者，检出率为1.50%（相互易位1.18%，罗伯逊易位0.32%）。不良孕产是平衡易位携带者主要临床表现，其早期自发性流产发生率为41.23%，女性携带者流产率高于男性，生育的活产儿占总妊娠数的50%，其中表型正常30.7%，表型异常19.3%；罗伯逊易位携带者胚胎丢失率高于相互易位携带者。少数平衡易位携带者有表型异常，主要表现为先天性多发性畸形、智能低下等，发生率为12.5%；对13例平衡易位携带者进行产前诊断，正常核型7例，携带者核型5例，染色体异常胎儿1例，表型异常者7例，占12.5％。提示减数分裂的联会互换产生不平衡重排配子，是导致平衡易位携带者不良生育的主要原因，部分平衡易位携带者有表型异常。羊水细胞培养染色体核型分析是安全、可行的产前诊断方法，产前诊断中对染色体平衡易位后代表型解释应慎重。

Study on chromosomal balanced translocation in strategy of better birth

In this study,chromosomal analysis of the cell samples from peripheral blood,amniotic fluid and human sperms has been performed using cytogenetic banding techniques accompanied with other clinical procedures of genetic counseling,prenatal diagnosis and follow-up survey so as to be able to clarify the possible influencing situation of chromosomal balanced translocation in better birth strategy.As a result,41 families with chromosomal balanced translocation (including 31 reciprocal translocation and 10 Robertsonian translocation)and 56 balanced translocation carriers found in 3727 questioned subjects,the detected rate of balanced translocation being 1.5%(1.18% for the former translocation and 0.32% for the latter separately). Secondly,increased risk of reproductive failure was demonstrated to be the leading clinical ma-nifestation of balanced translocation carriers.And the incidence rate of early spontaneous abortion was as high as 41.23% in comparison with that of normal population(15%).Meanwhile,the incidence rate of spontaneous abortion in female subjects was much higher than that in males.Concerning Robersonian translocation,its incidence rate of spontaneous abortion was significantly higher than that in reciprocal translocation.Furthermore, the live-birth number got access to 50% in the total of all the pregnancies of balanced translocation carriers,in which 30.7% showed normal phenotype and 19.7% showed abnormal phenotype.On the other hand,few subjects of balanced translocation were found to have abnormal phenotype,mainly presenting as congenital multiple malformations and mental retardation with the appearance rate of 12.5%.Finally,the prenatal diagnosis has been performed in 13 balanced translocation carriers and the results showed that there were 7 fetuses with normal karyotype, 5 with abnormal karyotype and 1 with chromosomal abnormality. Through these data,the conclusion could be made as follows:synapsis and crossing-over of chromosomes during meiosis might be considered as one of the principal causes of reproducing imbalanced re-arranged gametes which could result in reproductive failure and even yield abnormal offspring in carriers with imbalanced re-arrangement carriers. Therefore,phenotype abnormality may actually take place in few carriers with balanced translocation. So,karyotype analysis of cultured amniotic cells via amniocentesis should be a feasible ,precise and safe method of prenatal diagnosis to prevent from the appearance of imbalanced chromosomal offsprings although the karyotypic explanation for the offsprings of balanced translocation carriers should be made with much caution in prenatal diagnosis.