First Trimester Screen

First Trimester Screen

 

There are two parts to the first trimester screen: a blood test and an ultrasound. The screen occurs between 11 and 14 weeks of pregnancy. 

Please come to your appointment with a full bladder.

Checking for chromosome defects

The first trimester screen checks for:

  • Down syndrome or trisomy 21.
  • Edward’s syndrome or trisomy 18.
  • Patau syndrome or trisomy 13.

Brain and spinal cord problems are not checked with this test. Common problems with the brain and spinal cord are checked with an alpha fetal protein (AFP) test done later in pregnancy. The first trimester screen is more accurate than a quad screen to check for these specific defects, called chromosome abnormalities.

Having the test 

An abdominal ultrasound is done, and then a finger stick to get a blood sample. Gel is placed on the abdomen and a probe is used to measure your baby. Rarely, the ultrasound is done with a probe placed in the vagina. It is very important that you arrive with a full bladder for this test. 

The blood test, ultrasound and your age are used to measure the risk of your baby having one of the problems listed above. The results will be sent to your doctor in 5 to 6 days. Waiting for the results can cause anxiety and worry. Talk to your partner, health care provider and family about your feelings.

Test results 

The test is a screening only. It helps your doctor  measure the risk or chance of your baby having one of these chromosome defects.

  • A normal test result means you has a lower risk or chance of having one of these defects.
  • An abnormal test means you has a higher risk or chance of having one of these defects. More tests may be ordered to check for possible problems.

If more testing is needed 

Other testing may be done such as:

  • Blood tests to check the baby’s DNA in your blood.
  • A detailed ultrasound of your baby.
  • Testing a sample of the fluid around the baby, called amniocentesis.
  • Testing some tissue from the placenta, called a CVS (Chorionic Villus Sampling).

You may get genetic counseling to review the results.
 

© 2013 - October 23, 2020, The Ohio State University Wexner Medical Center.

This handout is for informational purposes only. Talk with your doctor or healthcare team if you have any questions about your care. For more health information call the Library for Health Information at 614-293-3707 or email: health-info@osu.edu.