Tests Available During Pregnancy
The following is a list of some common tests offered during pregnancy, and what is normally done with the results.
Laboratory tests offered to most pregnant women:
Blood Type and Rh Factor: If the Rh factor is Rh negative, RhoGam is given to protect future babies from becoming Rh sensitized, which can lead to anemia or even fetal death.
Hemoglobin: Used to detect anemia in the mother. Iron supplements may be used.
Sexually Transmitted Infections (Syphilis, HIV, Gonorrhea, Chlamydia, Hepatitis B and C, Herpes): Any bacterial infections identified would be treated with antibiotics to provide a cure for the woman and attempt to prevent infection of the infant. Viral infections may be treated to attempt to prevent infection of the infant.
Quad Screen: A four paneled test that screens for an elevated risk of specific genetic problems such as Down Syndrome or problems with the baby's spinal cord development. Women at increased risk would be offered diagnostic screening (amniocentesis).
First Trimester Genetic Screen: This test can be done earlier than the Quad screen to identify an increased risk of Down Syndrome or similar genetic disorders. The test is a combination of an ultrasound to measure nuchal translucency (or the thickness of the baby's neck) and a blood test. A woman with a positive screening test would be offered diagnostic testing (amniocentesis).
Rubella: A test used to identify whether or not a woman is immune to German Measles. Women who are not immune may be offered vaccination after delivery. Women who are not immune but are exposed or infected with German Measles may be offered additional testing.
Glucose Challenge Test: Used to identify women who may have gestational diabetes. Women with an elevated glucose level on this test then go on to take a Glucose Tolerance Test.
Group B Strep (GBS): Used to identify women who are carriers of a particular type of strep bacteria. Women who have these bacteria in their urine, vagina, or rectum are encouraged to use IV antibiotics during labor to prevent transmission of the bacteria to the baby and infection of the baby. This is a controversial issue. While routine testing and treatment of carriers has decreased the numbers of infants with serious GBS infection, many infants exposed to GBS would not become ill even without treatment. The use of antibiotics raises a risk of allergy to the mother. While the incidence of neonatal GBS infection has decreased, there may be an association with an increase in E-coli infections in infants over the same period. Nevertheless, the current consensus among women's and pediatric healthcare providers and the Centers for Disease Control and Prevention is that antibiotics be used. This is a good example of one of the many controversies in prenatal care.
Laboratory tests offered in special circumstances:
Glucose Tolerance Test: Used after an elevated glucose challenge test to diagnose gestational diabetes. Women with elevated levels on this test are given diet instructions and monitor their blood sugar. Medications such as insulin may need to be used to keep blood sugar normal.
Fetal Fibronectin Test: Used if a woman has symptoms of preterm labor, or has previously had a preterm birth, to help screen women at risk for preterm birth. While a negative test is reassuring, a positive test is less definitive, and may lead to treatment for preterm labor in some women for whom it is unnecessary.
Liver and Kidney Function tests: These tests may be used for women with symptoms of gestational hypertension, including high blood pressure or protein in the urine. They are used to help determine the severity of gestational hypertension.
Cystic Fibrosis Screening: This lab test identifies women who are carriers of the disease cystic fibrosis. If women are identified as carriers, their partners would be offered the screening test as well, to determine the chances of having a baby with cystic fibrosis.
Ultrasound: Most pregnant women are offered an ultrasound at least once during pregnancy. Ultrasound imagery lets an experienced practitioner identify the number of babies, the position of the baby, visualize the baby's organs and blood flow, estimate the age of the baby, locate the position of the placenta, determine the amount of amniotic fluid, and identify markers such as the baby's neck thickness that may be associated with genetic disorders. If complications develop during pregnancy, additional ultrasounds may be helpful.
Nonstress Test: This test may be offered as women reach or pass their due dates, or late in pregnancy for women who are over the age of 35. In the nonstress test, the baby's heart rate is monitored with an external fetal monitor. A nonreassuring test may be continued for a longer period, a biophysical profile may be done, or induction of labor may be proposed.
Contraction Stress Test: This test may be offered if a woman passes her due date, or if there are concerns about the baby's wellbeing or the functioning of the placenta. In the contraction stress test, the baby's heart is monitored while a woman is having contractions. If she is not having spontaneous contractions, pitocin or nipple stimulation may be used to induce contractions. A positive test means that nonreassuring changes in the heart rate occurred and further testing or induction of labor might be considered.
Biophysical Profile: This test may be offered to women who reach or pass their due dates, or who have nonreassuring findings on a nonstress test. The biophysical profile combines ultrasound and a nonstress test to provide an overall indicator of the baby's wellbeing. Four specific factors are indentified during the ultrasound, including the baby's movement, tone, "breathing" efforts, and the amount of amniotic fluid. Low scores on this test might mean that a labor induction would be recommended.
Chorionic Villi Testing: This test may be offered to women who are older than 35 and who want information about possible chromosome abnormalities earlier than can be achieved by using an amniocentesis. This test takes a sample of the chorionic villi (a part of the structures supporting the baby) and provides an analysis of the chromosomes. The test can be done at about 10 weeks after conception. Some women might choose pregnancy termination depending on the results of this test. The test itself may cause miscarriage or limb deformities of an otherwise normal baby.
Amniocentesis: This test may be offered to women who are older than 35, or to women who have positive screening results on the Quad Screen or First Trimester Genetic Screen. It is done by inserting a needle through the woman's abdomen into the uterus and takes a sample of the amniotic fluid. Chromosome analysis might be done, as with the chorionic villi testing. As the baby approaches its due date, amniocentesis might also be done to determine whether the baby's lungs are mature.