Midtrimester Amniocentesis : Experience of 2040 cases

Abstract

Objective To evaluate the validity of midtrimester amniocentesis.

Subjects Singleton pregnancies at risk of fetal chromosomal abnormalities, attending antenatal care clinic during June 1988- May 1997.

Main outcome measures Prevalence of abnormal fetal chromosomes and pregnancy outcomes.

Methods Amniocentesis and fetal cell culture were done between 15-24 gestational weeks and the subjects were followed until delivery.

Results A total of 2,040 high risk pregnant women underwent midtrimester amniocentesis. Only 1.2% was unable to obtain amniotic fluid. Among 2015 cases of successful amniocentesis, success rate of cell-culture was 92.5%. There were overall 1.88% (35/1864) of abnormal chromosomes. However, only 1.88% (35/1864) were proven to be abnormal, confirmed by either repeated amniocentesis, cordo centesis or sonographic features. Of these, 29 were electively terminated and 6 continued the pregnancies. Pregnancy outcomes in those with normal fetuses included spontaneous abortion 1.5%, dead fetus in utero 1.4%, premature deliveries 11.5%, term deliveries 85.7%.

Conclusion The incidence of abnormal fetal chromosome was 1.88%. The rate of fetal loss was similar to general population.