Clinical and cytogenetic findings on 31,615 mid-trimester amniocenteses

Since amniocentesis made prenatal diagnosis feasible in 1967, the method has become a popular tool in obstetric practices. In Korea, the demand for genetic counseling and prenatal tests has increased markedly because the number and proportion of pregnancies in women aged 35 yr and older have increased over a 20-yr period. Here we report clinical and cytogenetic findings on 31,615 mid-trimester amniocenteses. To investigate the changes in the annual number of amniocentesis, distribution of indications and age, and cytogenetic findings and abnormality rate according to indications, this study retrospectively analyzed 31,615 cases of mid-trimester amniocentesis performed at Seoul Clinical Laboratories, an independent medical laboratory center, during the past 13 yr (1994-2007). The annual number of amniocenteses has increased substantially since 1994. Among the 31,615 amniocentesis cases, the maternal age between 30 and 34 yr was the most common age group (35.4%). Among clinical indications, abnormal maternal serum screening results have been the most common indication for amniocentesis since 1994. Chromosomal abnormalities were detected in 973 cases (3.1%). Down syndrome was the most common abnormality found (36.9%, 359/973). In sex chromosomal abnormalities, 53 cases of Turner syndromes, 32 cases of Klinefelter syndromes, 20 cases of triple X syndromes, and 15 cases of 47,XYY were diagnosed. Of structural rearrangements, reciprocal translocations between two autosomes were the most common (15.5%, 151/973). Abnormal ltrasonographic findings showed the highest positive predictive value (5.9%) among the clinical indications. The present study could be used for the establishment of a database for genetic counseling. The discovery of an abnormality provides the option of termination or continuation in the pregnancy, a more suitable obstetric management in Korea.