Amniocentesis: A contemporary review

Abstract

Amniocentesis is an essential tool in obstetrics. Invasive testing remains the only modality for diagnostic genetic testing and the only way to provide comprehensive testing for chromosomal abnormalities. Despite increasing use of cell free fetal deoxyribonucleic acid (DNA) testing, amniocentesis should still be offered to all women who desire more complete and accurate genetic testing. Counseling patients on the limitations of screening tests is of the upmost importance and amniocentesis should continue to be recommended to confirm positive results from cell free fetal DNA testing or in the case of failed cell free fetal DNA test. As cell free fetal DNA screening has not adequately been studied in multiple gestations, its use is not recommended in this population and invasive testing should be offered. Amniocentesis is also very useful in providing additional information in settings other than genetic testing the second and third trimester. If intraamniotic infection is suspected, but the clinical findings are not enough to guide management, amniocentesis can provide testing that can both immediately clarify the picture (interleukin-6, gram stain, glucose levels) and finally confirm the presence of infection (culture). It can also be used to detect the presence of intrauterine viral infections. Additionally, amniocentesis may be used to test for markers of fetal lung maturity. The American Congress of Obstetricians and Gynecologists recommends that amniocentesis for this indication not be used in cases where late preterm delivery is indicated. It may be useful in guiding decision-making, however, when late preterm delivery is indicated, but when exact timing is unclear. Regardless of the indication, amniocentesis appears to be a relatively low risk procedure with minimal risk to the patient. Additional randomized controlled trials are not likely, as they are not feasible to due extremely high number of participants that would be needed to detect a difference in loss rates. Based on current literature, however, the risk of pregnancy loss from second trimester amniocentesis is low in both singleton and twin gestations. We counsel patients that technique has changed since the original studies in the 1970s and feel comfortable quoting a loss rate of 1/500-1/1000 based on contemporary data.

Keywords: Amniocentesis, Prenatal diagnosis, Invasive genetic testing, Procedure related loss rates, Cell free fetal DNA testing, Fetal lung maturity, Intraamniotic infection

Core tip: Invasive testing remains the only way to provide comprehensive testing for chromosomal abnormalities. Despite availability of cell free fetal DNA testing, amniocentesis should still be offered to all women who desire complete genetic testing. Amniocentesis is also useful if intraamniotic infection is suspected, but the clinical picture is unclear. Additionally, when late preterm delivery is indicated, amniocentesis need not be used. There are, however, some instances when delivery timing is unclear and amniocentesis for fetal lung maturity may provide information to guide delivery timing. Amniocentesis is a relatively safe procedure. We counsel patients that technique has changed since the original studies in the 1970s and feel comfortable quoting a loss rate of 1/500-1/1000 based on contemporary data.