Prenatal Diagnosis and Screening for Aneuploidy

Abstract

Genetic counseling should include comprehensive information on all modalities, advantages, disadvantages, and the gestational age for each test prior to screening. The positive predictive value of a screening test is greatly influenced by prevalence rates in the population tested. The aim of a screening test is to identify pregnancies at increased risk of being affected by a particular condition. Prenatal genetic diagnostic testing is able to definitively identify affected pregnancies. Prenatal diagnostic testing requires an invasive procedure, such as amniocentesis or chorionic villus sampling, to obtain a sample from the pregnancy to perform genetic testing. The decision to proceed with prenatal screening or testing is personal and based on an individual woman’s reproductive goals and desires. The discovery of cell-free DNA of fetal origin in maternal plasma opened up new possibilities for noninvasive maternal prenatal screening for fetal chromosomal aneuploidy.