Common Tests During Pregnancy: What To Expect

Regular prenatal office visits, blood testing, and ultrasounds set the groundwork for a healthy pregnancy and safe delivery of your baby. Over the next nine months, your OBGYN (Obstetrics and Gynecology) team will help you navigate your pregnancy journey, and recommend certain tests in each trimester.

Rochester Regional Health OBGYN, William Fletcher, MD, provides insight on the screenings, some of which are optional, that you should expect or consider during your pregnancy.

“During a pregnancy, the goal of every obstetric care provider is to optimize the health of both the person carrying the pregnancy and the baby. This helps to ensure the safest and healthiest outcome for both the pregnant person and newborn,” says Dr. Fletcher. “Prenatal care is the best way to ensure a good pregnancy outcome.”

Testing during the first trimester

With most pregnancies, office visits start at the end of the first trimester or early in the second trimester.  At these visits, we’ll check your blood pressure, monitor your weight, assess fetal growth, and listen to your baby’s heart rate.  In addition, here are some common tests that are offered during your first trimester:

6-8 Weeks

Although you’ve probably taken a few pregnancy tests at home by now – those double lines can be exciting to see – we’ll confirm your pregnancy during your first prenatal visit and establish your due date.

We‘ll also recommend basic urine and blood tests to screen for certain medical conditions, like anemia, and urinary tract infections.  If you are not sure when you may have become pregnant, or if you have irregular or infrequent menstrual periods, an ultrasound is typically ordered prior to or at this first visit. 

12 Weeks

The first few pregnancy visits often involve discussion of a lot of testing, and can sometimes feel overwhelming or confusing.  Rest assured, most of these tests are optional. If you find yourself confused about an available test or unsure of whether you want to pursue it, your provider can help clarify your options and give you additional resources to help you make a decision. 

Around 12 weeks, your OBGYN, nurse practitioner or midwife will discuss optional testing to see if you are at an increased risk of having a baby with a genetic disorder, such as Down Syndrome (Trisomy 21, or 3 copies of chromosome 21). You are not required to have this type of testing performed, but if you would like to, there are a few ways to do it.  

One way to screen for these conditions is for you to have a blood test that measures fragments of fetal chromosomes that are circulating in your blood.  This is called a cell-free fetal DNA test, and is typically offered to patients who are 35 years of age or older, as they are at a slightly higher risk of having a baby with these types of conditions.  Another way to test for these conditions is to do first trimester screening, a test that is usually offered to lower-risk patients and involves two steps:

• A blood test, which measures 2 hormone markers in your blood.
• An ultrasound to specifically measure the thickness of the space in the tissue that’s at the back of a baby’s neck (called nuchal translucency).

“The results of the blood test and ultrasound are used to determine whether or not a person is at increased risk of having a baby with one of these genetic conditions,” explains Dr. Fletcher.  "It’s important to understand that neither the first trimester test nor the cell-free fetal DNA test are diagnostic, meaning a positive result does not mean a baby has the condition. If your risk level is found to be high based on the results of these tests, the option of additional testing will be discussed, as this can help to determine with more certainty whether or not the baby actually has a genetic condition.”

If you have the cell-free fetal DNA test performed, you also have the opportunity to find out your baby’s gender if you opt to have screening for abnormalities of the sex chromosomes – ask your provider!  Unfortunately, the baby’s gender cannot be obtained from the first trimester screening (blood test and ultrasound) typically offered to people under age 35.  For this age group, the baby’s gender is usually determined during the anatomy ultrasound around 20 weeks of pregnancy.

Another type of genetic testing - called carrier screening - will also be discussed around this stage of pregnancy. This blood test will assess whether or not a pregnant person carries any of the genetic mutations associated with some of the more commonly seen inheritable genetic conditions, like cystic fibrosis or spinal muscular atrophy.  If both parents of a baby carry one of these mutations, the baby could inherit this type of condition, even if neither of the parents actually have it.  

Testing during the second trimester

During your second trimester, you’ll see your prenatal care provider for monthly visits. During these visits, your provider will monitor your health (weight, blood pressure, urine) and the well-being of your baby by listening to the fetal heartbeat.

15-20 Weeks

If you did not have genetic screening already done during the pregnancy but desire it, there is another opportunity to do it between weeks 15-22.  At this stage of pregnancy, genetic screening is done through a blood test, either the cell-free fetal DNA test mentioned above (for patients 35 years of age and older) or a Quad Screen, a blood test that measures 4 hormone markers in your blood. 

“Similar to the first trimester screening discussed above, the Quad Screen test also evaluates for the risk of Down Syndrome and other genetic conditions.  It’s again important to note that it is also not diagnostic, so a positive result does not mean a baby has a genetic condition.  Additional testing would likely be recommended,” says Dr. Fletcher. “One difference between the Quad Screen and first trimester screen is that the Quad Screen also evaluates the baby’s risk of neural tube defects such as spina bifida, as well as potential growth issues.” 

This is because one of the markers included in the Quad Screen is AFP - short for alpha fetoprotein.  This marker can be elevated in cases of spina bifida and related disorders.  The test also helps your provider assess your risk for gestational hypertension – high blood pressure in pregnancy – and a condition called pre-eclampsia.  Of note, AFP testing can be ordered separately for individuals who had genetic screening earlier in the pregnancy and would like to have it done.

20 Weeks

You’re halfway through your pregnancy! At this time, you’ll be scheduled for your level II sonogram, an exam conducted by our expert Maternal-Fetal Medicine specialists and the prenatal testing team.  This is a great chance to see your baby, and if you haven’t yet found out the baby’s sex, you can during this appointment.

Testing during the third trimester

Welcome to the third trimester…2 down, 1 to go! During the early part of the third trimester, your visits will likely increase in frequency, typically as often as every 2-3 weeks.  Starting at 36 weeks, many providers begin to see patients weekly until delivery.  At each third trimester visit, your provider will monitor your blood pressure and weight, assess your urine for protein and sugar to help screen for pre-eclampsia and diabetes, measure your uterus to assess fetal growth, and listen to your baby’s heartbeat.  

In addition, repeat ultrasound assessments may be recommended during this stage of pregnancy, particularly in patients with certain medical conditions (like high blood pressure or diabetes), or if there were certain findings on earlier ultrasounds that necessitate follow-up.  

Some individuals will also be asked to have non-stress tests during the third trimester, either early on for certain medical conditions or pregnancy complications, or toward the end of the pregnancy or after your due date.  This test assesses fetal well-being by analyzing the baby’s heart rate over a period of 20 minutes or more.  During this test, two monitors will be strapped around your belly as we listen to your baby’s heartbeat, monitor movement, and assess uterine contractions.

28 Weeks

Pregnancy hormones impact those expecting in all sorts of ways – including how your body processes insulin and sugar.

“Close to 10% of pregnant people will develop gestational diabetes,” says Dr. Fletcher. “During your visit around 26-28 weeks, we’ll give you a referral for a glucose challenge test. You’ll drink a very sweet beverage (it tastes a bit like overly sweet Gatorade), and after an hour you will be asked to provide a blood sample to check how your body has reacted to the sugar.”

If the results are positive, meaning that you may have gestational diabetes, you’ll be asked to come back for a longer glucose tolerance test to confirm the diagnosis. There is no need to fast or change your diet before the initial sugar test.

During this blood draw, your blood count will also be checked to assess for anemia and monitor your platelet count. Anemia is common in pregnancy. If you are anemic, your provider will discuss the severity and make any necessary recommendations to help with this condition. 

Lastly, for individuals with negative blood types, an antibody screen is done at the time of this blood draw as well to ensure you don’t carry antibodies that could pose a risk to the baby.

36 Weeks

You’ve hit the 8-month mark! During this visit, your doctor will perform your Group B Strep test.  This test involves passing a cotton swab along the skin at the opening of the vagina and the perianal area. This bacteria is a common skin bacteria present in about 1/3 of healthy adults and poses no health risk to you, but it can increase the risk of serious infections in newborn babies since they do not have a strong immune system at the time of birth.  If positive, your doctor will recommend you receive an antibiotic during labor to help minimize the risk of infection for your baby.

37+ Week

You made it to full term!  Your visits will continue to be frequent, and your provider will provide ongoing education about signs and symptoms of labor, preeclampsia precautions, and fetal movement.

You will likely also further discuss what to expect during labor and your hospital stay, and postpartum decisions like breastfeeding, decision to circumcise male infants, and a plan for birth control.

As you get closer to week 40, your provider may check your cervix if you seem close to labor.  As you near your due date or stay pregnant beyond your due date, your provider will likely discuss labor induction and work with you to formulate a plan to help keep you and your baby safe and healthy.

While it may seem far off for some reading this article, pregnancy often goes quickly and we look forward to caring for you and your growing family!