Prenatal diagnosis and outcome of pregnancy in 2036 women investigated by amniocentesis.

The report presents the indications for prenatal diagnosis, the results from amniocentesis and details of outcome of pregnancy in 2036 women. Aneuploidy was found in 26 fetuses (1.3%) including 16 with trisomy 21 and 9 sex chromosome abnormalities. There were 38 balanced chromosomal rearrangements (1.9%): 23 of these (1.1%) were pericentric inversions of a number 9 chromosome. Only two of the chromosomal abnormalities were found in other than those mothers referred for maternal age of 35 or over. Concern is expressed at the low referral rate for older mothers in the population served (only 25% of those over 40 years). Failure of amniotic cell culture occurred in 2.8% of cultures. Maternal cell contamination was detected in 23 cultures (1.1%) with four errors in reported fetal sex. Total error estimate was 0.5%. There were 20 in vitro artefacts (1.0%) with no reporting errors. Neural tube defects were identified in 28 fetuses and there were three false-positive and one false-negative results. Data on outcome of pregnancy was available from 1805 pregnancies (96.5%): 1295 were normal (71.7%) and 510 (28.3%) showed some abnormality. Pregnancy was terminated for fetal abnormality in 53 cases (2.9%) and fetal loss occurred in 65 (3.7%). Methods, quality control, safety and service considerations are discussed. It is suggested that amniocentesis should be restricted to centres where the greatest expertise is available. The service should be improved to meet the needs of a greater number of patients. The series is compared with other studies of over 1500 cases.