Here we explain the most common tests during pregnancy, what prenatal tests are used, and how testing is performed.
What Kinds of Routine Tests Are Performed During Pregnancy?
Several types of pregnancy tests are routinely given to pregnant moms. These are low-risk tests that can be easily done in your doctor’s office or health clinic. Many prenatal tests are specific to the first, second, or third trimester of pregnancy. Learn more about the stages of pregnancy here.
External Fetal Monitoring
At every prenatal visit, your doctor will use a fetoscope (a type of stethoscope) to measure your baby’s heartbeat. When it’s time for the baby’s birth, the nurse or doctor will strap a monitor to your belly to measure the baby’s heart rate.
Throughout your pregnancy, your doctor may order routine blood tests to measure the progress of your pregnancy, your health, and the health of your baby. For a blood test, your doctor will send an order to a phlebotomy (blood) lab, where a technician will take samples of your blood. The lab will send your sample to a bigger lab to look at the levels of markers and hormones. Your doctor will read the test reports and share this data with you.
Ultrasounds are a common kind of screening test for pregnant moms. There are a few types of ultrasound techniques: 2D, 3D, and 4D. Depending on the machines and training your hospital has, and the individual needs of your pregnancy, you may get one or more types of ultrasound tests during your pregnancy.
Two dimensional ultrasounds are the most common ultrasound tools. They take “flat” pictures of your uterus, cervix, and the baby.
A three dimensional ultrasound uses a special machine. The image gives data on the width, height, and depth of features in the images. This can be helpful for screening and diagnosis of certain conditions during pregnancy.
Four dimensional ultrasound is the latest advance in ultrasound imaging for pregnancy. 4D imaging lets the doctor see a constantly updated 3D image to make a “video” of the baby as he or she moves.
There are also two main ways of giving ultrasounds: transvaginal and abdominal ultrasounds.
Transvaginal ultrasound is usually done in early pregnancy. It uses a small ultrasound sensor in the shape of a wand that is coated with a slippery gel. The wand is placed in the vagina to get pictures of the cervix, uterus, and baby.
During an abdominal ultrasound, the healthcare worker puts gel on the belly and glides a small sensor over the gel to get pictures of the baby.
At most prenatal visits, your doctor will ask for a urine sample. You will urinate into a cup. The doctor will test the sample in the office or send it to a lab. Urine tests look for markers like blood cells, glucose (sugar), and proteins.
Glucose Challenge Test
Glucose challenge tests are commonly done during pregnancy to see how your body uses glucose (sugar). This helps your doctor know if you may need more tests to look at your risk of gestational diabetes, a form of diabetes that can develop during pregnancy.
In the glucose challenge test, you’ll need to drink a sugar mixture. One hour later, you will give a blood sample and your doctor will send the sample to a lab. If levels of glucose in your blood are high, your doctor will ask you to have a glucose tolerance test.
To learn more about common tests done during pregnancy, check out this FAQ sheet from the American College of Obstetricians and Gynecologists.
Less Common Prenatal Tests
In addition to routine tests and screenings during pregnancy, there are a few other tests that your doctor may ask you to take, depending on your risk factors and the results of your screening tests.
Glucose Tolerance Test
If your glucose challenge test shows high levels of blood glucose, your doctor will ask you to come in for a glucose tolerance test. For this type of testing, you’ll need to fast on the day of testing (only drinking water). You will give a blood sample. Then you’ll drink a sugar mixture. Over the next few hours, you’ll give more blood samples so your doctor can study the levels of glucose in your blood.
Genetic Screening and Diagnosis
Some genetic conditions can be found before birth. Your doctor may suggest genetic screening during pregnancy if you are in a high risk group. Moms who are at high risk include older mothers and those with a family history of genetic disorders.
Some of the birth defects that can be found with screening tests include:
- Down Syndrome
- Cystic fibrosis
- Spina bifida
- Fragile X syndrome
- Hemophilia A
- Polycystic kidney disease
- Sickle cell disease
- Tay-Sachs disease
You should note that screening and diagnosis for birth defects during pregnancy is optional. While many parents would like to know their child’s risk of certain birth defects in advance, some would rather not undergo this kind of testing before the birth of their child.
Learn more about the diagnosis of birth defects by visiting the CDC website.
If you and your doctor agree that it is warranted, they will perform an amniocentesis to look for certain genetic defects. This test involves placing a long, thin needle through your belly to take a small sample of amniotic fluid. Your doctor will use ultrasound images to guide the needle into the amniotic sac. They will send the sample to a lab for genetic testing.
Chorionic Villus Sampling (CVS)
Chorionic villus sampling involves taking a sample of the placenta and testing it for genetic defects.
Prenatal Cell-free DNA testing
Prenatal cell-free DNA screening, also known as noninvasive prenatal screening, is a newer method to screen for genetic defects. Because there are pieces of a baby’s DNA in each mother’s blood during pregnancy, this test can use a sample of the mother’s blood to look for problems with the baby.
Percutaneous Umbilical Blood Sampling
Percutaneous umbilical blood sampling, also known as cordocentesis, involves taking a sample of the baby’s blood from the umbilical cord for testing. It is not as common as amniocentesis or CVS.
Internal Fetal Monitoring
Sometimes, during the delivery, your doctor will need to perform internal fetal monitoring to learn more about your baby’s heart rate. For this test, your doctor will have to break your amniotic sac (bag of waters). They will then place a long tube through the cervix. The tube has a sensor on the end of it, which is put on the baby’s scalp to send heart rate data to a monitor.
What First Trimester Prenatal Screenings Will My Doctor Likely Perform?
First Trimester Ultrasound
In the first trimester, doctors use ultrasounds for several reasons:
- Nuchal translucency screening. This helps your doctor assess your baby’s risk of certain problems.
- Due date confirmation. Ultrasounds can give a more accurate due date than
- Multiple pregnancy determination. Ultrasounds will show the number of babies in your womb.
- Pregnancy health. Ultrasounds are helpful in checking your uterus and cervix and the health of your baby.
Your doctor will order a few blood tests in the first trimester. Blood tests in the first trimester include:
- Human immunodeficiency virus (HIV) test. It’s important to know your HIV status early in the pregnancy. The right treatment can prevent serious problems for both you and your baby.
- Screening for other sexually spread infections. These tests often include syphilis, chlamydia, and gonorrhea.
- Rh incompatibility test. If the Rh factor in your blood doesn’t match your baby’s, you can get treatment to make the pregnancy safer.
- Plasma protein A test. Plasma protein A is a hormone produced by the placenta. Abnormal levels could suggest a possible genetic defect.
- Human chorionic gonadotropin (hCG) test. hCG is another hormone made by the placenta. Abnormal levels are linked to a higher risk of genetic problems.
What Second Trimester Prenatal Screenings Will My Doctor Likely Perform?
Blood tests during the second trimester screening include:
- Hormone panels. These include estriol, inhibin, and hCG, all of which help give your doctor an idea of the health of your pregnancy.
- Alpha-fetoprotein screening (AFP). AFP is made by the baby’s liver. Abnormal levels of this protein can be a sign of issues like neural tube defects, Down syndrome, other genetic defects, multiple pregnancy (twins, triplets, etc.), or the wrong due date. If you have an abnormal AFP test, your doctor will ask you to get more testing done.
- PreTRM Test for Risk Management. At weeks 18 through 20, most asymptomatic women (no signs or symptoms of preterm labor, with intact membranes) with a singleton pregnancy can get the PreTRM Test to learn their risk of giving birth too early. Learn more about the PreTRM Test.
Second Trimester Ultrasound
Your doctor can do an ultrasound in your second trimester to confirm that your pregnancy is moving ahead well and to assess the health of your baby.
You and your doctor may decide that an amniocentesis is a good idea based on your risk factors or the results of other tests. The usual time for an amniocentesis is between the 15th and 20th week of pregnancy.
What Third Trimester Prenatal Screenings Will My Doctor Likely Perform?
Group B streptococcus screening
Group B streptococcus (GBS) is a bacterium found in the lower genital tract of about one-fifth of all women. If left untreated, it can cause problems in mothers and babies. Screening for GBS, usually with a urine sample, is done between weeks 35 and 37 of pregnancy.
Third Trimester Ultrasound
In the third trimester, an ultrasound can help your doctor check on the baby’s growth and position and measure the levels of amniotic fluid.
A glucose challenge test is usually given between weeks 24 and 28 to look at your body’s reaction to sugars. Abnormal results will show your doctor that you need for glucose tolerance testing. A glucose tolerance test helps your doctor know whether you may have gestational diabetes. Explore gestational diabetes resources from the American Diabetes Association.
Why Should the PreTRM Test Be Part of My Early Prenatal Testing?
A preterm birth—one that occurs before 37 weeks of gestation—is the leading cause of newborn death, and premature infants face a host of short and long-term medical problems. Learn more about preterm birth: check out Premature Birth 101 for moms.
Until recently, doctors had very few tools to try to predict each mother’s risk of preterm birth. The PreTRM Test for risk management is now available to most asymptomatic women (no signs or symptoms of preterm labor, with intact membranes) with a singleton pregnancy. It provides valuable insight, based on a simple blood test, about each pregnancy’s risk for early delivery. This can help your doctor give you the right support for your pregnancy.
With information from this prenatal test in hand, you and your doctor can take steps to prolong pregnancy, increase your fitness, improve your diet, possibly reduce your hospital stay, and improve your baby’s chances of a healthy birth. Check out the blog post, How to Prevent Premature Birth, to learn more about the steps you can take to give your baby the very best start in life.
Talk to your doctor today about the PreTRM Test for your individual risk assessment.