额外小染色体（mar）由Ellis等1962年首先报告〔1〕，以后在遗传咨询、外周血培养及羊水培养中均有发现。据报道，额外小染色体在一般人群中发生率低于1／1000〔2〕。我室在染色体检查中发现1例带有额外小染色体（mar）的病例，现报告如下：1临床资料病人女性，30岁，因不良孕 Additional small chromosomes (mar) were first reported by Ellis et al in 1962 [1], and later found in genetic counseling, peripheral blood culture and amniotic fluid culture. It is reported that the extra small chromosomes in the general population incidence of less than 1/1000 〔2〕. My room in the chromosomal examination found in 1 case with additional small chromosomes (mar) are reported as follows: 1 Clinical data Patient Female, 30 years old, due to poor pregnancy