Most women have healthy pregnancies, and their babies are born without difficulties. However, women with high-risk pregnancies often need to be closely watched for potential problems or complications. Fortunately, 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 first trimester include:
First trimester screen (also called sequential screen part one)
The first trimester screen (or sequential screen part one) is a combination of fetal ultrasound and maternal blood testing performed during your first trimester of pregnancy. The blood test detects pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG.)
The ultrasound exam focuses on measuring nuchal translucency, a thin layer of fluid at the base of the fetus’ neck. This screening process can help determine the risk for your fetus having certain birth defects including trisomy 21 (Down syndrome) and trisomy 18 (Edwards syndrome). This test is usually accompanied by a second blood test at 16 weeks gestation (sequential screen part 2) in order to obtain more reliable results.
Cell-free fetal DNA test
The cell-free fetal DNA test is done using a sample of a pregnant woman’s blood. The blood sample is analyzed for genetic material (DNA) that belongs to the fetus. Testing can detect abnormalities in fetal DNA that 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 the 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 that indicates abnormalities
Cell-free fetal DNA testing is only performed after 10 weeks gestation.
Chorionic villus sampling
Chorionic villus sampling (CVS) is a prenatal test that involves taking a sample of some of the placental tissue. This tissue contains the same genetic material as the fetus and can be tested for chromosomal abnormalities and some other genetic problems. This test can provide information about other genetic defects and disorders depending on the family history and the specific condition. CVS may be offered to women who are at increased risk for chromosomal abnormalities or have a family history of a genetic defect that is testable from the placental tissue. CVS usually is performed between the 10th and 12th weeks of pregnancy by a specialist from Maternal Fetal Medicine.