Prenatal Testing
Pregnancy is an exciting time in your life, full of wonder and anticipation. Wonder and worry go hand in hand, however, as you focus on the changes in your body and your baby’s development and growth. Prenatal testing helps ease some of the worry about your pregnancy and baby.
Prenatal care includes routine tests to gauge your health and your baby’s health throughout your pregnancy. Some tests are given to all women, while others may be given if problems put a mom or her baby at risk.
Some tests are repeated during the pregnancy. Blood, urine and cervical tissues are routinely tested in diagnostic labs. These tests can identify conditions, many of which can be treated during pregnancy to safeguard your baby’s health.
At your first prenatal visit, your urine sample is tested for bacteria that could cause an infection in your bladder or kidney. Your urine is tested at every visit to check for sugar, which could be a sign of diabetes, or protein, which could alert your healthcare provider about an infection, kidney disease, or problem with high blood pressure. The cervix is examined at your first visit and a Pap test may be done to check for changes in the cells of the cervix that could lead to cancer.
Blood tests during your first prenatal visit check for anemia, blood type, and Rh factor. If you have Rh-negative blood and your baby has Rh-positive, your body might make antibodies that attack the baby’s blood. Rh-negative moms require special care throughout pregnancy.
Other blood tests screen for rubella antibodies. Rubella is also known as German measles and can be dangerous to unborn babies. If you have not had rubella, you must avoid anyone who has the infection. After your delivery, you should be vaccinated to immunize against the disease. Blood tests also can screen for HIV (the virus that causes AIDS), the liver infection hepatitis B, and the sexually transmitted disease syphilis. If you have any of these conditions, you can be treated to reduce the risk to your baby.
A maternal serum screening test, sometimes called the “triple screen,” is done between the 15th and 18th weeks of the pregnancy. This test measures the levels of alpha-fetoprotein produced by the baby and two of the mother’s hormones, human chorionic gonadotropin and estriol. Abnormal results may indicate a higher risk for certain birth defects such as Down syndrome or neural tube defects such as spina bifida. If these tests are abnormal, your doctor may refer you to a high-risk specialist for additional testing including an ultrasound exam or amniocentesis.
Amniocentesis is a procedure that tests the fluid surrounding the baby. During an ultrasound exam, the doctor inserts a thin needle through the mother’s abdomen and takes out a small amount of amniotic fluid that goes to a lab for genetic testing. The results of this test will help your doctor understand your baby’s condition.
Chorionic Villus Sampling (CVS) is a very specific test for chromosomal problems or genetic birth defects and is offered to mothers who have a higher risk for a baby with a genetic abnormality. This test is done between 10-12 weeks gestation. During a vaginal exam, cells from the developing placenta are removed and sent to a lab for testing.
Glucose tests are done between 24 and 28 weeks. For this test, the mom drinks a special sugary liquid, and her blood is drawn one hour later. If the blood sugar level is too high, another similar test lasting three hours can diagnose gestational diabetes.
You also may be screened for group B streptococcus (GBS) during the last few weeks of your pregnancy during a vaginal exam. Anyone can carry group B Strep. This common bacterial infection is not usually a problem to adults but can be life threatening to newborn babies. If your screening culture comes back positive for GBS, you will be treated with intravenous antibiotics during labor and delivery to protect your baby’s health.
Many healthcare providers offer ultrasound examinations, which can give mothers and fathers an exciting first look at their unborn children. During this exam, a device called a transducer is gently moved across the top of your tummy or in some cases inserted into the vagina. Sound waves from the transducer produce an image of your baby on a screen. The ultrasound test can check for the baby’s age and look at the brain, spinal cord, heart, kidneys, and fluid around the baby to detect problems. An ultrasound can be done at any time during the pregnancy, but the anatomy scan results may be limited before 20 weeks gestation.
Nonstress testing is used in high-risk pregnancies or in a low-risk pregnancies when a mom goes past her due date. The external fetal monitor is used to watch for changes in the baby’s heart rate while the baby is resting as well as moving. A biophysical profile combines the nonstress test with ultrasound observation.
A problematic prenatal test result may not mean your baby is in trouble, but it will give your health care provider the information needed to provide you with specialized care. Prenatal testing has limitations. Some common birth defects – including cleft lip and palate and some heart problems – cannot be determined by lab tests, ultrasound, or amniocentesis. Not every test is perfect. Your baby might have a problem that the test was not designed to pick up, or your baby may not have the condition the test shows. It is important to learn about these tests. If you have concerns about whether you should have certain prenatal tests, talk them over with your partner and healthcare provider.
The good news is that most babies are born healthy, and prenatal care can help ensure a good start for your child.