Types of screening tests

Prenatal screening tests for genetic conditions include:

• First trimester screening tests. During your first trimester, your healthcare professional can offer a blood test and an ultrasound. The blood test measures certain substances in your blood. The ultrasound measures the size of the clear space in the tissue at the back of your baby's neck. This type of ultrasound is called a nuchal translucency test. In Down syndrome and some other genetic conditions, the nuchal translucency measurement is larger than usual.
• Second trimester screening tests. During your second trimester, your healthcare professional may offer another blood test called the quad screen. This test measures the levels of four substances in the blood. Results show your risk of carrying a baby who has certain genetic conditions caused by chromosome changes. These conditions include Down syndrome and trisomy 18. The test also can check for a higher risk of conditions that involve the brain or spinal cord. These are called neural tube defects. Another second trimester screening test is a routine ultrasound of your baby's anatomy. This ultrasound is recommended for every pregnancy.
• Prenatal cell-free DNA screening. This blood test can be done in any trimester. It checks the baby's DNA in the pregnant person's bloodstream. It looks for a higher risk of specific genetic conditions such as Down syndrome and trisomy 18. This screening test also can provide information about a baby's sex.