Lab Tests During Pregnancy

June 26, 2017

Hematocrit tests for the presence of anemia. It is regularly done during the 28th and 34th week office visits. If you have anemia, you will be asked to take more of your iron supplement, and your hematocrit will be checked more frequently. Occasionally, we will require more tests to check for other possible causes of anemia.

Urine Tests
Urine tests are conducted at each prenatal visit to check for nitrites (chemicals) and leukocytes (white blood cells), substances and cells that indicate infection in the urinary system. Additionally, we will examine your urine for evidence of glucose and protein, substances that can indicate early diabetes and toxemia, respectively.

Antibody Titers
Antibody titers check the level of antibodies contained in the blood. A test is done to determine whether the mother’s blood contains antibodies that may be harmful to the unborn child. This is most commonly a problem in Rh negative mothers. If you have Rh negative blood, these tests will be performed routinely during the 28th and 34th week visits. Additionally, we now offer the protective injection RhoGAM to Rh negative mothers during the 28th week of pregnancy.

Triple Screen
Triple screen can detect abnormal blood values during pregnancy, which may indicate a fetus with a higher than normal chance for open neural-tube defects (anencephaly and spina bifida) and Down’s Syndrome. This test is normally done at 16–18 weeks of pregnancy. Your physician or nurse midwife will talk to you about having the test done.

One-Hour Glucose Tolerance Test
One-hour glucose tolerance tests check the level of glucose in your blood one hour after drinking a specific amount of sugar. This allows us to determine whether your body is handling glucose normally during your pregnancy or if you are developing gestational diabetes. Gestational diabetes occurs in 5–7% of all pregnancies.

Urine Culture
Urine cultures detect the growth of bacteria in your urine and will be done if other routine screening tests indicate a possible infection.

Hepatitis Screening
A hepatitis screening checks for evidence of a past occurrence of hepatitis. You should definitely tell us if you have a history of any type of hepatitis since certain types may be passed on to your fetus and would require the baby to have treatment immediately after her/his birth.

Gonorrhea, Chlamydia, and Herpes

Gonorrhea, chlamydia, and herpes are venereally (sexually) acquired infections. There are tests that can easily determine their presence.

AIDS stands for Acquired Immune Deficiency Syndrome; it is a disease that prevents the body from fighting off infection and illness. The virus may be transmitted from mother to baby during pregnancy. All women should receive AIDS tests.

Cytomegalovirus Antibody Test (CMV)
Cytomegalovirus is a common virus that carries little risk to adults. However, the virus can cross the placenta and cause serious difficulties for the fetus. The test for CMV determines whether you (and your fetus) are immune to the virus.

Ultrasound uses high frequency sound waves to produce an image of the uterus, placenta, and baby. Ultrasound was developed in the late 1940s, and in the last 20 years, equipment suitable for office use has been developed. The procedure is considered safe during pregnancy.
Possible reasons for ordering this test include

• unclear pregnancy dates,
• suspected multiple pregnancy (twins),
• uterus that is larger or smaller than expected for a certain stage of pregnancy,
• examination of the placenta when bleeding occurs during pregnancy, or
• suspected abnormal position of the baby.

In addition, ultrasound may be used to determine the baby’s well-being by studying the baby’s activity, breathing, movements, and amount of amniotic fluid. An ultrasound machine is available in our office should the need arise. We are able to provide this service at a lower cost than the hospital charges, and most patients find our service more convenient.

Group B Strep
Group B strep can be cultured from the vagina in 15–20% of women. At about 33–36 weeks of pregnancy, we will check for the presence of this bacteria. If the culture is positive, we will treat you at the time of labor with antibiotics to protect your baby.

Biophysical Profile
A biophysical profile combines an ultrasound procedure and a non-stress test. An array of fetal physical activity such as breathing, arm and leg motion, and the volume of amniotic fluid can be assessed with ultrasound. Combining the information learned from these studies with the non-stress test, we can more completely determine how healthy your baby is while still in the uterus.

Amniocentesis obtains a sample of the amniotic fluid surrounding the baby by placing a needle through the abdominal wall and uterus and applying suction with a syringe to remove that fluid. Insertion of the needle using ultrasound guidance is usually done after the administration of a local anesthetic.

In early pregnancy, this is done to obtain some of the cells from the baby. These cells are then grown in a culture and can be studied for chromosome defects and a variety of other inherited genetic diseases. Possible reasons for ordering this test include

• maternal age over 35,
• a history of babies with certain birth defects, or
• a family history of certain hereditary diseases.

If you have a family history of hereditary disease or previous babies with birth defects, you should discuss this with our staff to determine if this testing would be appropriate for you.

Late in pregnancy, this test may be performed to determine if the baby’s lungs are mature enough for the baby to be delivered. This may be required when scheduling a repeat cesarean section and the dates are uncertain, or when complications of pregnancy make it desirable to deliver the baby before labor begins.

This test may also be performed if an Rh negative mother has developed antibodies that could potentially harm her baby.

Risks of the procedure include premature labor, development of Rh incompatibility, infection of the amniotic fluid, bleeding from the placenta, and injury to the baby.

All of these risks taken together occur less than 1% of the time. Amniocentesis should not be used to satisfy curiosity about your baby’s sex before birth.

Non-Stress Test

Non-stress tests are other tests for fetal well-being that do not require drug intervention and can be performed in our office. Fetal well-being is determined by measuring the fetal heart rate in response to the baby’s activity. An increase in fetal heart rate is a positive sign indicating fetal well-being. If the baby does not increase its heart rate in response to its own activity, it is common to proceed to the contraction stress test.

Contraction Stress Test with Nipple Stimulation
This stress test may be performed before a contraction stress test with Pitocin is performed (refer to the next item). Stimulating the nipples of a woman in the later pregnancy weeks may cause contractions, and these will help us to evaluate the health of the baby while still within the uterus.

Contraction Stress Test with Pitocin
Conditions such as diabetes, high blood pressure, fetal growth retardation, and prolonged pregnancy pose a threat to your unborn baby. In the event that these conditions are present, an intravenous infusion of Pitocin is given until you develop three contractions within a 10-minute period. When this stress test is deemed necessary, it is usually performed at the hospital. The baby’s heart rate is electronically monitored to determine the effects of the contractions. A negative result occurs when the heart rate stays normal during contractions; this a good sign that your baby is doing well and should tolerate labor. If an abnormal heart rate appears, the meaning is less clear, but it may mean that the baby may not tolerate the stresses of labor, making a delivery by cesarean necessary.

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