Testing During Pregnancy – Second Trimester

Learn about tests you may have during the second trimester of your pregnancy.

There are many tests and procedures to monitor your health and your baby’s health. Many of these tests pose little or no risk and can provide tremendous amounts of information to doctors, midwives and expectant parents. Some types of testing and procedures, however, do carry some risk for mother, baby or both. You should discuss any concerns you have with your LVHN health care provider. 

Tests commonly used during the second trimester include:

Amniocentesis

Amniocentesis obtains a small sample of amniotic fluid that surrounds the fetus. It helps diagnose chromosomal disorders and open neural tube defects such as spina bifida. This test also can provide information about other genetic disorders, depending on family history and specific condition.

Amniocentesis generally is offered between 15 and 20 weeks of pregnancy if you are at increased risk for chromosome abnormalities, such as being over age 35 at delivery, or having an abnormal maternal serum screening test. Amniocentesis is performed by a specialist from Maternal Fetal Medicine.

Cell-free fetal DNA test

Cell-free fetal DNA test uses a sample of a pregnant woman’s blood to detect genetic material (DNA) that belongs to the fetus. Fetal DNA abnormalities may indicate certain chromosomal conditions, including trisomy 21 (Down syndrome,) trisomy 18 (Edwards syndrome), trisomy 13 (Patau syndrome) and sex chromosome abnormalities. Women who are considered at increased risk for having a child with a chromosomal condition may be offered this test. Criteria include:

  • Advanced maternal age (age 35 or older at time of delivery)
  • Abnormal results from maternal serum screening, such as a sequential screen or quad screen
  • Previous pregnancy that resulted in birth of child with chromosomal condition
  • Fetal ultrasound indicates abnormalities

Cell-free fetal DNA testing can be done any time in the second trimester, in addition to late first trimester.

Quad screen

This second trimester screening blood test measures:

  • Alpha-fetoprotein (AFP, a protein made by all babies)
  • Unconjugated estriol (a type of estrogen produced by the fetus)
  • Human chorionic gonadotropin (hCG, a hormone produced by the fetus and placenta)
  • Inhibin A (a hormone produced by the placenta)

These markers provide information about your risk for having a baby with an open neural tube defect such as spina bifida, or a chromosomal condition such as trisomy 21 (Down syndrome) or trisomy 18 (Edwards syndrome). This screening is performed by taking a sample of your blood between 15 and 20 weeks of pregnancy (16th to 18th is ideal).

Second trimester screen (also called sequential screen part two)

Second trimester screen is a follow-up blood test to sequential screen part one that takes place during the first trimester. Sequential screen part two tests for:

  • Alpha-fetoprotein (AFP)
  • Unconjugated estriol (a type of estrogen produced by the fetus)
  • Human chorionic gonadotropin (hCG, a hormone produced by the fetus and placenta)
  • Inhibin A (a hormone released by the placenta)

Results from sequential screen part two are combined with the results from sequential screen part one and can determine the risk of a baby having an open neural tube defect such as spina bifida, or a chromosomal condition such as trisomy 21 (Down syndrome) or trisomy 18 (Edwards syndrome). When you have both first and second trimester screening tests performed, the tests’ ability to detect an abnormality is greater than using just one screening independently. Most but not all cases of Down syndrome can be detected when both first and second trimester screening are used.

High-risk pregnancy care

LVHN offers leading-edge maternal fetal medicine services – 24 hours a day, 7 days a week – for high-risk pregnancies.

Learn more

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