Detection of chromosome aberrations in the second trimester using genetic amniocentesis: experience during 1995-2004

To retrospectively investigate the 10-year experience of prenatal diagnosis of fetal chromosome aberrations by second-trimester amniocentesis.

Data were collected at Taichung Veterans General Hospital between 1995 and 2004 from cytogenetic analyses of cultured amniocytes from second-trimester amniocentesis. The main indications for amniocentesis included advanced maternal age, abnormal maternal serum screening results, and abnormal ultrasound findings. Chromosome aberrations included autosomal aneuploidies, sex chromosome aneuploidies, polyploidies, and rearrangements. Variant chromosomes were considered to be normal and excluded.

A total of 7,028 amniocenteses were performed and analyzed for chromosome aberrations. Among these, 4,026 (57.29%) were for advanced maternal age, 1,500 (21.34%) for abnormal maternal serum screening results, 553 (7.87%) for abnormal ultrasound findings, and 949 (13.50%) for other reasons. The highest detection rate of chromosome aberrations was in cases undergoing amniocentesis for abnormal ultrasound findings (8.86%), followed by other reasons (2.74%), abnormal maternal serum screening results (2.60%), and advanced maternal age (2.31%). Chromosome aberrations were detected in 207 cases (2.90%), including fetuses of 93 older mothers, 39 mothers with abnormal serum screening results, 49 mothers with abnormal ultrasound findings, and 26 mothers with other reasons for amniocentesis. Of fetuses with chromosome aberrations, 144 (69.56%) had trisomy 13, trisomy 18, trisomy 21, or sex chromosome disorder. The other 63 cases (30.44%) included balanced translocation, unbalanced abnormality, inversion, and marker chromosome.

For daily practice, our data could offer a database for proper genetic counseling, such as termination issues and future pregnancies.