An overview of testing when pregnant
A wide array of screenings and exams are offered during pregnancy. Your care team will collect urine samples throughout pregnancy, and you’ll have blood drawn to scan for anemia, blood type, HIV and other conditions. You will also likely have a pelvic exam and multiple ultrasounds. The patient is the center of all decision-making regarding testing, as each pregnancy and delivery is unique.
When do you get your first pregnancy ultrasound?
Your first pregnancy ultrasound typically takes place during the first appointment of your pregnancy. A sonographer will scan the abdomen to confirm pregnancy, verify gestational age and determine if you’re carrying multiples.
Pregnancy blood tests and urine tests
Blood draws and urine tests during your first trimester are important for the health of mother and baby. These can include:
- Blood type and antibody screen: It is recommended women who are Rh negative receive a medication called Rhogam during pregnancy so that they don’t develop an anti-D antibody.
- Complete blood count (CBC): This test looks at the composition of your blood by percentage of types of cells. It is important especially to know red cell levels, which could signal anemia, and levels of platelets, which are important for blood clotting. A high white blood cell count while pregnant may mean that your body is fighting an infection.
- Rubella titer: Rubella is another name for German measles, which if contracted during pregnancy can cause birth defects, including hearing and vision loss, or miscarriage. This test will show if a woman is immune to the disease.
- Hepatitis B screening: Hepatitis B is a virus that affects the liver. It can be transmitted sexually or through needle sharing, contact with infected blood and body fluids, and — rarely — blood transfusions. If a mother has Hepatitis B, then her baby will need to receive special medication as well as immunization at birth to reduce the risk of transmission.
- Syphilis screening: Syphilis is a sexually transmitted disease that fortunately has become less common. Syphilis can cross the placenta and cause birth defects for baby, but is highly treatable in the mother.
- Human Immunodeficiency Virus: The Centers for Disease Control and Prevention recommend HIV testing in pregnancy, and for many women this will be the first time they are tested. HIV transmission from mom to baby can be significantly reduced with medications.
- Gonorrhea and chlamydia: A urine sample or a cervical swab will test for gonorrhea and chlamydia, sexually transmitted diseases that often cause no symptoms, but which can cause eye infections in babies and increase the risk for a mother’s water breaking prematurely, low birth weight and preterm birth. Both are very treatable with antibiotics.
Expert care for you and your baby
Genetic carrier screenings
Genetic testing can be performed prior to becoming pregnant, during pregnancy or once baby is born. During or pre-pregnancy, genetic carrier screening can be performed using blood samples from both partners to determine the risk of having a child with an early-onset disease (for example, cystic fibrosis, sickle cell anemia, spinal muscular atrophy and Tay Sachs disease).
Even healthy adults can be carriers of genetic abnormalities, and when both partners have the same ones, their offspring are much more likely to have the disorder.
“We now have more expansive and accurate genetic screening than ever before,” said Brighton Goodhue, a certified genetic counselor and member of the high-risk pregnancy team at Vanderbilt Women’s Health. “That said, genetic testing is entirely optional. If you choose any type of prenatal genetic testing or screening, we’ll be with you every step of the way.”
Non-invasive prenatal testing
Once you become pregnant, non-invasive prenatal screening is another optional blood test that screens for common genetic conditions such as trisomy 21 (Down syndrome), trisomy 13 (Patau syndrome) and trisomy 18 (Edwards syndrome). It also allows you to find out the baby’s sex.
“This test is also known as cell-free DNA screening,” Goodhue said. “It works by analyzing small fragments of genetic information from the placenta that can be detected in the maternal bloodstream during pregnancy.” Non-invasive prenatal testing cannot definitively confirm or rule out a chromosome abnormality. However, results reported as “low risk” indicate a 99% chance that a pregnancy is not affected with common chromosomal or abnormalities.
More about genetic testing
Advances in genetic testing for pregnant women
New screening gives pregnant women a less-invasive route for prenatal genetic testing.
What to know about genetic testing surrounding pregnancy
If you’re pregnant or trying, your provider will likely offer a referral for genetic testing. Here’s what to know about this optional workup.
What is universal carrier screening and why should I have it?
A blood test can reveal whether parents are carriers for certain genetic diseases.
Second trimester ultrasound
Between 19 and 22 weeks, you’ll have a mid-trimester scan, during which a sonographer will measure your baby’s growth and see how the baby is doing.
“The 20-week scan is focused on evaluating the fetal anatomy and checking that your baby is growing appropriately,” said Sybil B. Tremblay, a registered diagnostic medical sonographer at Monroe Carell Jr. Children’s Hospital at Vanderbilt.
The sonographer will assess:
- Key anatomy, including heart structures, the brain and internal organs
- Anatomical measurements such as head circumference, abdominal circumference and length of the long bones
- Position of the placenta and where it connects to the umbilical cord
- The amount of amniotic fluid in the uterus
- Fetal behavior and activity
- Blood flow patterns, which might be color-coded in red or blue to show the direction of the blood flow
- The baby’s sex
If the ultrasound is abnormal or shows a possible anomaly, you will be referred to a maternal-fetal specialist to reassess and confirm with another ultrasound. At this appointment, you will speak to a maternal-fetal medicine doctor about the ultrasound findings. Depending on the diagnosis, you may also meet with other specialized providers along with a genetic counselor and a social worker. You will learn more about your baby after the birth. Until then, an ultrasound can give valuable information so the team can provide the best care possible.
What is amniocentesis?
“An amniocentesis is a procedure where you sample the baby’s amniotic fluid,” said Dr. Rolanda Lister, a maternal-fetal medicine specialist with Vanderbilt Women’s Health. “Typically an amniocentesis is done to get genetic information or if there is concern for an infection.” Guided by an ultrasound, your doctor will insert a needle through your abdomen, uterus and amniotic sac to sample the fluid, which can then be sent off to the lab for various tests.
This test can help diagnose various genetic conditions and fetal abnormalities, including Down syndrome, cystic fibrosis, muscular dystrophy, sickle cell disease and more. Your doctor may recommend an amniocentesis if a previous pregnancy was affected by one of these conditions, if you have a family history of one of them or if a prenatal screening showed a high risk.
With amniocentesis, there is a small risk of pregnancy loss, less than 1% when in the second trimester. If you have a bloodborne disease such as HIV or Hepatitis C, there may also be a risk of disease transmission to the fetus.
Glucose test for gestational diabetes
Testing for gestational diabetes will usually take place at the 24- to 28-week prenatal visit. Your doctor will provide a fluid to drink (usually orange- or lime-flavored) that contains concentrated glucose. An hour after you drink it, blood sugar is checked to determine glucose tolerance. Women who are obese or have a history of gestational diabetes with a previous pregnancy may have a glucose check done earlier in the pregnancy, during the first trimester.
If you screen positive for gestational diabetes, you will be referred for an appointment with a diabetes educator, who will teach you how to check your blood sugar levels daily. Working with a nutritionist can also help with choosing the proper foods to eat during pregnancy to manage your blood sugar levels.
Group B strep testing in pregnancy
During the third trimester, your provider will conduct a swab for Group B streptococcus, a type of bacteria. If it’s positive, your obstetric care team will give medicine during labor to lower the chance that the baby gets the bacteria. In these final months, you will also continue to have regular urine tests and may also have repeat testing for anemia, HIV and other conditions.
Why parents choose genetic testing
A large majority (85%) of pregnant women in the U.S. consider testing and discuss it with their providers. About 40% of women decide to have genetic testing done during pregnancy. Genetic testing can be performed on baby after birth, too, if health problems or defects are present. This is especially helpful for patients who value that information but don’t feel comfortable undergoing more invasive procedures during pregnancy.
“It can be helpful to know about certain conditions, such as heart defects, prior to birth, when there’s not a time crunch to treat a baby who is really sick,” said Emily Franciskato, a reproductive genetic counselor with Vanderbilt Women’s Health. “But genetic testing is never something that people should feel like they have to do. If information is something that people feel like empowers them and any choices that they make, that’s what it’s for.”
