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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. Also see first trimester screens and tests, which includes a list of questions to ask at your appointment. Keep track of your tests on this prenatal screen and test record.

    Screen or test Why it may be offered

    Amniocentesis: Using ultrasound, 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 concer may be related to your age, family history, the results of a screen, or other factors. The AFP is measured to help identify if your baby has an "open" type of defect of the spine, like spina bifida.

    This diagnostic 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.

    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 trisomy 18. Those who are at high risk are offered amniocentesis to determine if there really is a problem.

    An increased AFP level helps identify most babies with openings in the skull, spine (spina bifida) or abdomen.

    This screen is usually offered at 15 to 18 weeks. ACOG supports this option for all pregnant women.

    Ultrasound

    This ultrasound will assess the well-being of your baby. It will evaluate your baby's size and position in your uterus, your ovaries and cervix and the number of babies. It may also be able to tell you the gender of the baby.

    It may also identify birth defects. Ultrasound is not perfect and not all birth defects will be recognized with ultrasound.

    It is usually done around 20 weeks of pregnancy.

    Cervical evaluation (cervical length ultrasound): This is an ultrasound designed to look at the length of your cervix. It typically uses a vaginal transducer to get the most accurate measurement of your cervix. If you have a history of preterm birth or cervical procedures/surgery, you may have more frequent evaluations of the length of your cervix between 16 to 24 weeks of pregnancy. This may help determine your risk for preterm delivery. A shortened cervix may lead your doctor to recommend additional treatment.

    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 26 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.

    Sequential (or integrated) screening: This test combines measurements from two blood tests and a first trimester ultrasound.To estimate the chance that a baby will be born with Down syndrome, trisomy 18, or an open neural tube defect such as spina bifida.