Who should consider first trimester screening?
First trimester screening is available for women of any age but is designed to increase detection of fetuses with these specific chromosomal abnormalities in primarily low risk individuals with singleton gestations. Women who have additional risk factors such as a positive family history or who are older than 34 years of age (advanced maternal age) should undergo genetic counseling, and should be offered consideration of diagnostic testing such as chorionic villus sampling (CVS) or genetic amniocentesis. If such at risk patients elect not to undergo diagnostic testing, first trimester screening may be offered to further assess pregnancy specific risk. How are results interpreted? What follow-up testing is needed? Every screening result will assign a numerical risk of having an affected fetus, including a separate risk for trisomy 21 (Down syndrome) and trisomy 18. If the first trimester screening result is normal or negative, additional testing should include second trimester maternal
