Incidence of chromosome abnormalities at a second-trimester genetic amniocentesis for Mainland Chinese women of advanced maternal age: a study of 6, 584 cases

摘要

Objective: The aim of this study was to calculate the expected incidence of chromosomal aneuploidy at second trimester genetic amniocentesis in Mainland China in women aged 35 and older.Methods: We reviewed the genetic amniocenteses data in Peking Union Medical College Hospital between January 2001 to June 2011.The indication for genetic amniocentesis was solely advanced maternal age (AMA).A total of 6,584 cases were included in this study.The AMA women was divided into two groups by maternal age,the group of 35-39 years old and the group of ≥40 years old.The incidence of fetal Down syndrome was compared between the two groups by chi-square test.Results: A total of 121 cases were diagnosed to be chromosomally abnormal,giving an overall incidence of 18.38‰ (121/6,584).The abnormal karyotypes included 111 cases of various aneuploidies and 10 cases with various structural abnormalities.The aneuploidies(mosaicism included)were 59 cases of (47,+ 21),25 cases of (47,+ 18),2 cases of (47,+ 13),8 cases of (45,X),3 cases of (47,XXX),13 cases of (47,XXY) and 1 case of (47,XYY).The karyotype of (47,+21) was the most frequent chromosomal abnormality,with an overall incidence of 8.96‰,account for 53.1％ of all aneuploidies.Sex chromosome aneuploidies were the next most common,with a total incidence of 3.80‰.The incidence of fetal Down syndrome was significantly higher in the group of ≥40 years old than that of the group of 35-39 years old (P=0.047).Conclusions: The incidence of chromosomal aneuploidy found in this study is the first data published for Mainland China and will be helpful for the counseling of pregnant women in this age group.Consideration may be given to prenatal screening versus prenatal diagnosis in women of advanced maternal age in Mainland China.