Second trimester: Prenatal screens and tests you may be offered

Test	Why it may be given
Amniocentesis A small amount of amniotic fluid is withdrawn from the sac around your baby under careful ultrasound observation by the doctor; your baby's cells are grown in culture and the chromosomes are studied. Other DNA or biochemical tests may be done if your history indicates.	This is given to women age 35 or older to check for chromosomal disorders (such as Down syndrome). Or to those identified at risk for specific genetic disorders where a test exists. Typically done at 15 to 18 weeks.
Antibody screen Blood is drawn and tested.	This identifies some antibodies in your blood. If your test is positive, you may need more testing. Also, you may receive a preventive shot at this time, if you are Rh negative (See Rh factor).
Fetal fibronectin (fFN) test A special swab will be used to take a sample of your vaginal discharge (like during a Pap test).	If you are having contractions, this test can help tell if your contractions are the kind that will cause your baby to be born prematurely. Fetal fibronectin is a glue-like substance that connects the amniotic sac around your baby to the inner wall of your uterus. If you are between the 23rd and 34th weeks of pegnancy and your health care provider finds fFN in your vaginal discharge, you are at increased risk of having your baby early.
One-hour glucose screen from a finger stick and tested for the amount of glucose. You do not need to fast for this test.	This test measures the likelihood of you developing gestational diabetes. If the result is positive, your health care provider may recommend the three-hour glucose tolerance test. Done at 24 to 28 weeks.
Three-hour glucose tolerance test Your blood is drawn, you drink a sweet drink, and then your blood is drawn once an hour for 3 hours (bring something to read!). You eat normally the day before, then fast overnight.	This test is done if the one-hour glucose screen is positive. It tests for diabetes during pregnancy. (See gestational diabetes.)
Multiple marker screen Blood is drawn from your arm and tested for the presence of three or more proteins produced by your baby and the placenta. This test is also known as the triple test or quadruple test.	This is designed to try to identify most babies with spina bifida; to identify women who may be at risk for third trimester complications; and/or to provide a parent with a more precise assessment of the chance the baby may have Down syndrome or other chromosome problems. Typically done at 15 to 20 weeks. If positive, special diagnostic tests are available to clarify.

Questions to ask

Ask your health care provider these questions when considering the tests listed on this page:

• What do you hope to learn from this test?
• If the test is positive, what's next?
• If the test is normal, could my baby still have a problem?
• If I am carrying a baby with Down syndrome, what are the chances I will have a normal test?
• If the test is positive, how likely is it my baby has a problem?
• What alternatives are there to having this test?

Related Links

Prenatal screens and diagnostic tests

Prenatal screenings and tests record (requires Adobe Reader)

Prenatal care: Seeing your provider often

Allina Pregnancy Care

Pregnancy & Parenting eMagazine: Starting your second trimester, Month 4

Second trimester

First published: 10/04/2002
Last updated: 06/19/2003

Reviewed by: Allina Patient Education experts