ACOG Committee Opinion #296: first-trimester screening for fetal aneuploidy

First-trimester screening for chromosomal abnormalities offers potential advantages over second-trimester screening. Studies in the 1900s demonstrated an association between chromosomal abnormalities and the ultrasonographic finding of abnormally increased nuchal translucency (an echo-free area at the back of the fetal neck) between 10 and 14 weeks of gestation. First-trimester screening using nuchal translucency, free beta-hCG, and pregnancy-associated plasma protein-A has comparable detection rates and positive screening rates for Down syndrome as second-trimester screening using 4 serum markers (alpha-fetoprotein, beta-hCG, unconjugated estriol, and inhibin-A). Although first-trimester screening for Down syndrome and trisomy 18 is an option, it should be offered only if certain criteria can be met.

Published by Obstetrics and gynecology, 2004. The guideline itself is at the source linked here.

pubmed.ncbi.nlm.nih.gov/15229041/