First-Trimester Screening For Birth Defects

Test Overview

During the first trimester of pregnancy, screening tests for birth defects may be done. These tests look for possible problems with your baby. The tests may be called first-trimester screening, combined first-trimester screening, or the combined screening.

The screening tests show the chance of your baby having certain birth defects such as Down syndrome or trisomy 18.

First-trimester screening tests include:

Blood tests.

These measure the level of two substances in the blood called pregnancy-associated plasma protein A (PAPP-A) and beta-human chorionic gonadotropin hormone (beta-hCG). PAPP-A is a protein in the blood. Beta-hCG is a hormone made by the placenta.

Nuchal translucency test.

This test uses ultrasound to measure the thickness of the skin at the back of your baby's neck. An increase in the thickness can be an early sign of Down syndrome.

In some cases, the doctors look at the combined screenings that you've had over a period of time. This is called an integrated screening. It's done in two stages at two different times during the pregnancy.