Routine Prenatal Testing: What Happens During Each Trimester

Here’s what to know about some of the tests you can expect over your 40-week journey.

The Importance of Routine Prenatal Visits

Regular prenatal care can help improve your chances of having a healthy pregnancy and delivering a full-term baby. You’ll meet with your doctor or midwife many times throughout your pregnancy to monitor how things are going. While each pregnancy is unique, the typical schedule of prenatal visits typically goes as follows:

• Weeks 8 to 28: A checkup once every four weeks
• Weeks 28 to 36: A checkup once every two weeks
• Weeks 36 to 40+: A checkup once a week

This schedule of visits helps to ensure that you complete the screenings that closely monitor how things are going. “Routine prenatal screening allows for detection of any conditions that may adversely affect mother and baby,” explains ChenChen Sun, M.D., a board-certified ob-gyn at Tufts Medical Center in Boston. This information can help you optimize your care along the way.

That said, “This might be the first time in your life where you have monthly or even weekly medical visits, which can be a little bit anxiety-provoking,” adds Ilina Pluym, M.D., a board-certified ob-gyn at UCLA Health in Los Angeles, California.

Learning more about the types of screenings you’ll undergo with each visit may help ease some of those anxious feelings.

What to Expect During Each Prenatal Visit

When you’re pregnant, just about every prenatal visit you attend will include a:

• Urine sample, to check for a urinary tract infection and monitor glucose levels, which, if elevated, could be a sign of gestational diabetes. They’ll also check for protein in the urine, which could be a sign of preeclampsia
• Weight check, to make sure your baby is growing and you’re maintaining a healthy weight gain
• Blood pressure check, to monitor for preeclampsia.

Your doctor may also use a fetal doppler to listen to your baby’s heartbeat at some or all visits.

Based on how far along you are in your pregnancy, you may undergo additional screenings and/or tests that take place outside these routine checkups. It’s important to work with your doctor to determine which screenings are most important for you (and whether or not any are optional).

Your First Prenatal Visit

“At your very first visit, you're going to get the most comprehensive exam by your physician,” explains Pluym. That includes:

• A full medical history and family health history of both biological parents (if you know it).
• A full physical exam, including a pelvic exam, as well as a Pap smear (if you’re due for one).
• Urinalysis and blood tests, including screening for sexually transmitted infections or diseases.

“That's really just to make sure you’re starting off the pregnancy as healthy as possible,” she explains. “It’s going to check for infections, predisposing conditions, anything that could put the baby at risk.” The idea is to make your pregnancy and baby as healthy as possible.

First-Trimester Screenings and Tests

Your first trimester is defined as weeks one through the end of week 13 of pregnancy. During this time, your doctor may recommend the following tests and screenings:

• Rh factor screening. You may undergo blood work in the first trimester to determine your blood type and test for the Rh factor (Rhesus is an inherited protein found on the surface of red blood cells). If you’re Rh negative and your baby is Rh positive, you will need treatment to prevent your body from creating antibodies that can put your Rh positive baby at risk.
• Genetic carrier screening. If you didn’t do any genetic screening prior to getting pregnant, your doctor may recommend a screening test for both biological parents to determine if either one of you is a carrier for certain genetic conditions, which may increase your baby’s risk of genetic abnormalities. Sun says: “The preconception and early pregnancy period is a good time for you to ask your family about family history, so that your doctor can best determine what, if any, additional testing would be recommended for you.”
• Noninvasive prenatal testing (NIPT). Your doctor may also recommend this simple blood test once you’re pregnant for early detection of chromosomal abnormalities. “NIPT, or the cell-free DNA test, is typically performed starting at 10 weeks,” explains Sun. This is a screening, not a diagnostic test, so depending on the results obtained from NIPT, your doctor may recommend additional testing.
• Ultrasound. “Most women have an ultrasound around seven to 10 weeks,” explains Pluym. This is known as the dating ultrasound, which measures the fetus. The measurements and the date of your last menstrual period will be used to confirm your estimated due date.
• First trimester screening. This is a test typically done between weeks 11 and 14 and includes a blood test checking hormone levels along with a special ultrasound called a nuchal translucency that measures the thickness of your baby’s neck. This is a screening test that reports the risk your baby could have Down syndrome or another chromosomal abnormality. Depending on the results of the first trimester screening, your doctor may recommend diagnostic testing, which can give you more definitive answers.

Second-Trimester Screenings and Tests

Your second trimester is defined as weeks 14 through the end of week 27 of pregnancy. During this time, your doctor may recommend the following tests and screenings:

• Blood tests: A specific type of blood test known as the maternal blood screen, or quadruple screen test (quad screen), is typically performed between weeks 15 and 22 of pregnancy to detect your baby’s risk of birth defects.
• Ultrasound: “Everybody gets a big ultrasound around 20 weeks,” explains Pluym. Also known as the anatomy scan, this is the most important ultrasound of your pregnancy, as it checks the development of your baby’s organs and body parts.
• Amniocentesis: If results from previous screenings indicate increased risk, your healthcare provider may recommend an amniocentesis to confirm whether or not your baby has a birth defect or genetic condition. This test is typically done between weeks 15 and 20. It comes with a small risk of complications, as it involves taking a sample of amniotic fluid from around the baby. As such, undergoing the test is optional.
• Glucose challenge test: This test measures your blood sugar levels to assess your risk of gestational diabetes. It involves consuming a sugary drink and having your blood sugar levels measured with a blood test after an hour. This screening is typically done between weeks 24 and 28 of pregnancy, and if blood sugar levels are high, a three-hour test called the glucose tolerance test may be done to rule out or confirm a diagnosis of gestational diabetes.

Third-Trimester Screenings and Tests

Your third trimester is defined as weeks 28 through 40 (and beyond) of pregnancy. During this time, your doctor may recommend a few more screenings and/or tests, such as:

• Group B strep: This test screens for a type of bacteria that typically isn’t an issue for the mother, but, if passed along to the baby, may pose health risks. It involves a swab to check cervical fluid for the bacteria, and is typically done between weeks 35 and 37 of pregnancy. If you test positive, you’ll be given antibiotics during labor to protect the baby from infection, explains Pluym.
• Ultrasound: Depending on concerns highlighted in any previous tests, or the practice of your doctor or midwife, “you might have another ultrasound in the third trimester,” says Pluym. This ultrasound checks your baby’s growth and determines if they are in a head-down position in preparation for labor.

“​Your doctor may recommend additional testing based on prior obstetric history and personal history,” explains Sun.

Preconception Genetic Screening

Genetic screenings for birth defects are optional and a personal choice. Some people wish to know in advance about these types of things so they can make informed decisions; others prefer not to know. Letting your healthcare provider know about your personal preferences can help you determine which screenings to skip.

How to Prepare for Each Visit and Follow-Up

Before each visit, take time to think about how you’ve been feeling. “I recommend you bring up your questions and concerns with your healthcare provider,” advises Sun. You may want to write down your questions so you can arrive at your visit with a list. This helps you stay organized and ensures all of your questions will be addressed.

After each visit, be sure to go over any test results with your provider—especially if you receive test results electronically. “A lot of times, things will flag as red, but the lab doesn't know if you're pregnant or not,” explains Pluym. “Always wait for your physician to interpret your results for you, because our reference ranges might be different for pregnancy.”

Remember: Most pregnancies end with healthy babies. “​It is a new and exciting time, and there will certainly be a lot of unknowns,” adds Sun. But all the screenings and tests will have been worth it once you’re holding your new bundle of joy.

You May Also Like:

• The First Trimester: A Guide to Early Pregnancy
• The Second Trimester: A Guide to Midpregnancy
• The Third Trimester: A Guide to Late Pregnancy
• The Fourth Trimester: A Postpartum Guide to Life with a New Baby