Common Tests During Pregnancy
The following are some of the more common tests done during pregnancy:
First trimester prenatal screening tests
First trimester screening is a combination of fetal ultrasound and maternal blood testing. This screening process can help to determine the risk of the fetus having certain birth defects. Screening tests may be used alone or with other tests.
There are 3 parts of first trimester screening:
Ultrasound test for fetal nuchal translucency (NT). Nuchal translucency screening uses an ultrasound test to examine the area at the back of the fetal neck for increased fluid or thickening.
Two maternal serum (blood) tests. The blood tests measure 2 substances found in the blood of all pregnant women:
Pregnancy-associated plasma protein screening (PAPP-A)--a protein produced by the placenta in early pregnancy. Abnormal levels are associated with an increased risk for chromosome abnormality.
Human chorionic gonadotropin (hCG)--a hormone produced by the placenta in early pregnancy. Abnormal levels are associated with an increased risk for chromosome abnormality.
When used together as first trimester screening tests, nuchal translucency screening and maternal blood tests have a greater ability to determine if the fetus might have a birth defect, such as Down syndrome (trisomy 21) and trisomy 18.
If the results of these first trimester screening tests are abnormal, genetic counseling is recommended. More testing such as chorionic villus sampling, amniocentesis, cell-free fetal DNA, or other ultrasounds may be needed for accurate diagnosis.
Second trimester prenatal screening tests
Second trimester prenatal screening may include several blood tests, called multiple markers. These markers give information about a woman's risk of having a baby with certain genetic conditions or birth defects. Screening is usually done by taking a sample of the mother's blood between the 15th and 20th weeks of pregnancy (16th to 18th is ideal). The multiple markers include:
Abnormal levels of AFP may signal:
Open neural tube defects (ONTD), such as spina bifida
Down syndrome
Other chromosomal abnormalities
Defects in the abdominal wall of the fetus
Twins--more than one fetus is making the protein
A miscalculated due date, as the levels vary throughout pregnancy
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