First Trimester Screening
First trimester screening combines fetal ultrasound and maternal blood testing, and is performed during the first three months of pregnancy.
What is first-trimester screening for?
This screening process can determine the fetus’s risk of having certain congenital disabilities, including Down syndrome, trisomy 13, or trisomy 18. First-trimester screening is just a simple screen, and a positive result will need to be discussed within the context of the specific results.
What does the screen entail?
There are three parts to this screening:
- Ultrasound test for fetal nuchal translucency (NT). This screening uses an ultrasound test to examine the area at the back of the fetal neck for thickening or increased fluid.
- Pregnancy-associated plasma protein-A (PAPP-A). This is one of two maternal serum blood tests. PAPP-A is a protein produced by the placenta in early pregnancy. Abnormal levels of this protein are associated with an increased risk for chromosome abnormality.
- Human chorionic gonadotropin (hCG). This is the second maternal serum blood test. hCG is a hormone produced by the placenta in early pregnancy. Abnormal levels are also associated with an increased risk for chromosome abnormality.
When these tests are combined, they have a greater ability to determine if your fetus might have a congenital disability. If you do get abnormal results, additional testing may be necessary for an accurate diagnosis.
How is the first trimester screening performed?
- First-trimester screening generally occurs between the 10th and 14th weeks of pregnancy.
- During the procedure, an ultrasound (usually transvaginal) is performed to examine the fetus.
- Blood is then drawn from the mother’s vein and is sent to a lab for analysis.
This screening is only performed to determine if there is an increased risk of congenital disabilities. It can also help to identify women who may need additional monitoring or testing during pregnancy.