本文认为对出生的Down 综合征患儿进行细胞遗传学检查是必要的,因其复发风险取决于异常染色体的存在。不管母龄多大,在所有Down 综合征患儿中有92.5%是原发性三体征—47,XX(XY),+21,4.8%是易位型以及2.7%属嵌合体(46,XX/47.XX,+21或46,XY/47,XY,+21)。具有21q/21q 新发生易位的Down 综合征的复发风险可能低至1/100以下。但作者报道了有21q/21q 易位Down 综合征的两个家庭连续罹患的情况。第一个家庭当母龄22岁,父龄24岁时出生Down 综合征患儿(妊娠37周产,第二胎第二产,出生时体重3.15kg)。周围血染色体计数33个细胞, This article suggests that cytogenetic examination of children with Down syndrome is necessary because the risk of recurrence depends on the presence of anomalous chromosomes. Regardless of age, 92.5% of all children with Down syndrome had primary trisomy -47, XX (XY), +21, 4.8% were metathesized and 2.7% were chimeras (46, XX / 47.XX, +21 or 46, XY / 47, XY, +21). Down syndrome with a 21q / 21q neo-translocation may have a low risk of recurrence of up to 1/100. However, the authors reported a series of consecutive episodes of two families with the Down syndrome of 21q / 21q. The first family was born with a Down Syndrome (37 weeks of gestation, a second child, 3.15 kg at birth) when the mother was 22 years old and her father was 24 years old. Peripheral blood chromosome counts 33 cells,