WellSpan Home

Health Library

First Trimester Screening

What is first trimester screening?

First trimester screening combines fetal ultrasound and blood tests for the mother. It’s done during the first trimester of pregnancy, during weeks 1 to 12 or 13. It can help find out the risk of the fetus having certain birth defects. This includes chromosome defects such as Down syndrome (trisomy 21), or trisomy 18 or 13.

First trimester screening may include:

  • Ultrasound test for fetal nuchal translucency (NT). This test uses ultrasound to look at the back of the fetus' neck. It checks for increased fluid or skin thickening. These might mean a defect.
  • Blood tests. The blood tests measure 2 substances found in the blood of all pregnant women:
    • Pregnancy-associated plasma protein-A (PAPP-A). This protein is made by the placenta in early pregnancy. Abnormal levels could mean an increased risk for a chromosome defect.
    • Human chorionic gonadotropin (hCG). This hormone is made by the placenta in early pregnancy. Abnormal levels could mean an increased risk for a chromosome defect.
  • Cell-free fetal DNA screening. This tests the baby's DNA that is in your blood. It checks for certain abnormal chromosomes. It can also check for defects in the fetal sex chromosomes (X or Y). Cell-free fetal DNA screening does not find structural birth defects, such as spina bifida or defects in the abdominal wall. 

If first trimester screening is abnormal, you may need more testing for diagnosis. This may include chorionic villus sampling, amniocentesis, or another ultrasound.

Why might I need first trimester screening?

First trimester screening can tell if the fetus might have a birth defect. The screening test is usually offered to all pregnant women toward the end of the first trimester. Cell-free fetal DNA testing may be offered to women at increased risk, such as women over age 35. These screening tests may not be accurate in women with a multiple pregnancy (twins or more).

What are the risks of first trimester screening?

First trimester screening involves an ultrasound and blood tests. These are low-risk tests. But if the tests are not done at the right time during the pregnancy, the results may be wrong. For example, this might happen if your due date was miscalculated. This can cause unnecessary worry and concern for you and your partner.

First trimester screening is not 100% accurate. It’s only a screening test to see if there is an increased risk for a birth defect. It also helps to see if you need more testing or monitoring during your  pregnancy.

False-positive results can show a problem when the fetus is actually healthy. False-negative results show a normal result when the fetus actually does have a health problem.

How do I get ready for a first trimester screening?

You don't need to do anything special to get ready for the ultrasound or blood tests.

What happens during a first trimester screening?

First trimester screening generally involves the following tests. They are done between weeks 10 and 14:

  • Ultrasound test. Usually a transvaginal ultrasound is done to look at the fetus. In this test, a small ultrasound transducer is inserted into the vagina.
  • Blood test. Blood is drawn from a vein and sent to the lab for analysis.  Cell-free fetal DNA blood testing may be done as early as 9 weeks. 

What happens after a first trimester screening?

After the tests are done, you will meet with your healthcare provider to review the results. First trimester screening is not 100% accurate, and does not give a diagnosis. If the results are abnormal, your healthcare provider will discuss follow-up testing for a diagnosis. If appropriate, you will be offered genetic testing and counseling.

Next steps

Before you agree to the test or the procedure make sure you know:
  • The name of the test or procedure
  • The reason you are having the test or procedure
  • The risks and benefits of the test or procedure
  • When and where you are to have the test or procedure and who will do it
  • When and how will you get the results
  • How much will you have to pay for the test or procedure
First Trimester Screening - WellSpan Health

Online Medical Reviewer: Bowers, Nancy, RN, BSN, MPH
Online Medical Reviewer: Freeborn, Donna, PhD, CNM, FNP
Last Review Date: 2015-07-25T00:00:00
Last Modified Date: 2016-07-28T00:00:00
Published Date: 2016-07-28T00:00:00
Last Review Date: 2007-03-30T00:00:00
© 2016 WellSpan Health. All Rights Reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

Are you sure you would like to cancel?

All information will be lost.

Yes No ×

About the provider search

This search will provide you with WellSpan Medical Group and Northern Lancaster County (Ephrata) Medical Group primary care physicians and specialists. If we don’t have a WellSpan Medical Group physician to meet your criteria, the search will expand to include community physicians who partner with WellSpan Medical Group physicians through the WellSpan Provider Network or provide care to patients on the Medical Staffs of WellSpan’s Hospitals.


Schedule Your Next Appointment Online with MyWellSpan

Use your MyWellSpan patient portal any time to view available appointments, and pick the date and time that best suits your schedule.

Go to MyWellSpan

New to this practice?

If you don't have a WellSpan primary care provider and would like to schedule a new patient appointment with a provider who is accepting patients, just log into your MyWellSpan account, and go to the Appointment Center section. As you progress through the scheduling process, you will be able to see the offices that are accepting new patients in relation to your zip code. If you are not enrolled in MyWellSpan, go to https://my.wellspan.org, call 1-866-638-1842 or speak with a member of the staff at a participating facility to sign up. New patient scheduling not available at all practices/programs.

Already a patient at this practice?

If you already have a relationship with a WellSpan practice, simply log into your account, and go to the Appointment Center section. As you progress through the scheduling process, you will be able to schedule an appointment with any provider or practice that already counts you as a patient. Online scheduling varies by practice/program.