Martin-Bell综合征,是一种X连锁的智力低下,与X染色体长臂远端被称为X_q27·3脆性位点的细胞遗传学标记有关。自1981年,有些人利用这种标记的存在对此类智力低下开展了产前诊断。由于检测X染色体脆性位点需要特殊的培养条件,培养基内必须没有或含极低量的叶酸及胸腺嘧啶,而且在处理过程中可使供分析的分裂相数目减少或导致染色体破坏,因而在羊水细胞检测标记的X染色体尚存在一定困难。但在淋巴细胞,尽管不是胎儿淋巴细胞,检测X_q27脆性位点的方法已经很好的建立,故作者决定取胎儿血样对有脆性X染色体的X连锁智力低下症进行产前诊断,并与从同一妊妇采 Martin-Bell syndrome, an X-linked mental retardation, is associated with cytogenetic markers called the X_q27.3 brittle site distal to the long arm of the X chromosome. Since 1981, some people have used this marker to make prenatal diagnosis of such mental retardation. Because of the special culture conditions required to detect fragile sites on the X chromosome, there must be no or very low levels of folic acid and thymine in the culture medium, and the number of cleavage phases available for analysis may be reduced or the chromosome destroyed during processing, Amniotic fluid cell detection of X-chromosome markers still have some difficulties. However, in lymphocytes, though not fetal lymphocytes, the detection of X_q27 fragile sites has been well established, so the author decided to fetus fetus blood samples of X-linked frivolous X-linked mental retardation prenatal diagnosis, and with the same Pregnant women mining