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Prenatal Testing: Common Tests During Pregnancy

From the moment a woman finds out she is pregnant until the baby is born, many prenatal tests must be conducted to ensure the mother and child are both healthy.

Pap Smear

An initial pelvic exam, or pap smear, is done to check for gonorrhea, chlamydia, vaginosis and for any abnormal cells indicating cervical cancer. These conditions can affect the health of both mother and baby and must be detected as soon as possible to start treatment.

Blood Tests

Throughout the course of pregnancy a woman will have her blood tested several times. In the first trimester this is done to determine the woman’s blood type, especially whether she is Rh positive or negative. If the mother is found to be Rh negative, a Rhogam shot may be given around 28 weeks and within 72 hours of delivery. This shot should ensure that the mother’s blood is compatible with any future babies she may carry (so that both will be Rh positive). In addition to checking blood type, initial blood samples will be tested for anemia, diabetes, HIV, hepatitis B, syphilis, rubella and chicken pox immunity.

Urine Tests

Urine samples will also be taken several times throughout pregnancy. Every time a pregnant woman visits the doctor/midwife, her urine will be checked for the presence of protein and infection. Urinary tract infections happen to be more common during pregnancy and must be treated immediately so as not to endanger the fetus. If protein is found in the urine, it can indicate a serious condition called preeclampsia, a type of high blood pressure that pregnant women develop. This must also be addressed as soon as possible.

Triple or Quadruple Screen Test

In addition to the routine blood and urine tests mentioned above, a woman has the option of undergoing the triple screen test, also known as multiple marker screening. This test is conducted between weeks 13-16 and involves a simple blood draw. The blood is tested for alpha-fetoprotein (a protein made by the baby’s liver and secreted into the mother’s blood), human chlorionic gonadotropin (hCG, a hormone produced within the placenta) and estriol (a female sex hormone produced by the placenta and the fetus). These substance levels are checked to determine if the baby has a spinal cord problem, kidney or urinary tract problems, abnormal gastrointestinal system, Turner Syndrome, Down’s Syndrome, Tay-Sachs disease, cystic fibrosis or red blood cell problems.

Although the triple screen test detects 80-90% of the babies with spinal cord problems and 60% of those with Down’s Syndrome, it is sometimes considered controversial, because many of the babies who test positive actually do not have any such problems. Moreover, if a baby tests positive, the further tests required, such as amniocentesis or chorionic villus sampling, may threaten the baby’s health or they can be very expensive, e.g. cell-free fetal DNA testing. The triple screen test is recommended to women who are over 35, have a family history of birth defects, have had a premature baby, miscarriages or stillborn baby, had a viral infection or have used harmful medications during pregnancy and have diabetes.

Ultrasound

The most exciting test a pregnant woman will undergo is probably the ultrasound. This test is typically performed between weeks 11-14 and then 20-26 to reveal the baby’s size, gender, health and due date. In case of a high-risk-pregnancy, the ultrasound test will be performed several times during pregnancy.

Glucose Screen Test

Shortly after the second ultrasound, around weeks 24-28, the mother will have a glucose screen test, also known as a glucose challenge test. This test enables the woman to know whether she is developing gestational diabetes. The woman drinks a glucose solution on an empty stomach and then has a blood sample drawn within one hour. If she has gestational diabetes, her health and the baby’s health must be monitored more closely because they are at higher risk of developing problems such as macrosomia.

Group B Strep Screening

One of the final tests pregnant women will have done occurs between weeks 35-37. They will be tested for Strep B, a common infection in pregnant women. If the mother is found positive, she will be given antibiotics to prevent passing the infection to her baby.

Where to Get More Information: American Pregnancy Association