Your Guide to Prenatal Tests
The what, when, and why of 30 pregnancy exams, screens, and scans
First Trimester Screening
Who: Available to all women
When: Between 10 and 14 weeks, although usually between 11 and 13 weeks
How: This screening has two parts: a blood test to measure levels of two pregnancy-specific hormones (beta hCG and PAPP-A) and an ultrasound exam to measure the fluid beneath the skin at the back of the fetus’ neck (nuchal translucency). Using your age and the results from those tests, your healthcare provider can assess your personal and immediate risk of carrying a baby with specific chromosomal abnormalities, which will be given to you as a risk of, say, 1 in 800 or 1 in 4,000.
Why: To screen for trisomy 21 (Down syndrome, which causes mental retardation) and trisomy 18 (Edwards syndrome, which causes more severe retardation and is often fatal by age 1), and sometimes trisomy 13 (Patau syndrome, which often causes congenital heart disease) earlier than standard second-trimester testing. It does not evaluate the risk of neural tube defects such as spina bifida.
Results and follow-up: If your results show a high risk of an abnormality, your doctor may recommend further testing, such as a chorionic villus sampling (CVS) or amniocentesis, to confirm the diagnosis. But don’t panic—your results only indicate a possible risk. Most likely, your baby is fine.