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Beginnings: Pregnancy, Birth & Beyond

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Second trimester: Screens and tests

During this trimester, you are likely to see your health care provider every month. At these visits you will be offered some screens and tests, and possibly an ultrasound.


Screen or test Why it may be offered

A doctor removes a small amount of the amniotic fluid that surrounds your baby. This fluid contains your baby's cells. These cells are grown in a culture, and the chromosomes are studied. The fluid is also checked for AFP, which is a protein your baby makes. If your family history indicates additional concerns, other DNA or biochemical tests may also be done.

It is used to determine if your baby has a specific chromosome problem. The concern may be related to your age, family history, use of assisted reproductive techniques, the results of a screen, or other factors. The AFP is measured to help identify if your baby has an "open" type of defect like spina bifida. This procedure is usually done between 15 and 18 weeks. American College of Obstetricians and Gynecologists (ACOG) supports this option for all pregnant women.

Amniocentesis can be used later in pregnancy to test for lung maturity.

Fetal fibronectin (fFN) test
A swab is used to get a sample of the discharge from your vagina. This is checked for the substance fibronectin.

If you are having contractions between 23 and 34 weeks, the presence of fibronectin indicates you are at risk for preterm labor.

Multiple marker screen
Blood is drawn from your arm and tested for several proteins made by your baby and the placenta. Currently these proteins include AFP, HCG, estriol, and inhibin.

These measurements can help identify most women who are at increased risk of carrying a baby with Down syndrome and some other chromosomal problems. Those who are at high risk are offered amniocentesis to determine if there really is a problem. This screen also helps identify most babies who may have spina bifida and some other problems with the spinal cord and brain. This screen is usually offered at 15 to 18 weeks. ACOG supports this option for all pregnant women.

One-hour glucose screen
One hour after you drink a very sweet drink, your blood is tested for the amount of glucose.

To screen for gestational diabetes, the kind of diabetes that can develop during pregnancy. It is done at 24 to 28 weeks. If this screen is positive, a three-hour glucose tolerance test is recommended.

Three-hour glucose tolerance test
Your blood is drawn and tested before you drink a sweet drink. Then, your blood is drawn and tested once an hour for three hours.

To determine if you have gestational diabetes. This test is more sensitive than the screen and requires that you fast overnight.

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 screen?
  • If the screen is positive, how likely is it my baby has a problem?
  • If the screen is positive, what happens next?
  • If the screen is normal, how likely is it that my baby could have the problem?
  • What alternatives are there to having this screen?


Source: Allina Health's Patient Education Department, Beginnings: Pregnancy, Birth and Beyond, sixth edition, preg-ahc-90026, ISBN 1-931876-25-8

First published: 10/04/2002
Last updated: 08/22/2011

Reviewed by: Allina Health's Patient Education Department experts