A pregnant woman gets ready for the group B strep test.
The group B strep test is one of the last procedures you’ll undergo during pregnancy. (For Spectrum Health Beat)

As your pregnancy progresses, your OB appointments will change.

During the first few months of pregnancy, you’ll typically visit your provider every four weeks, then every two weeks during the last few months. In the final month, you’ll see your OB weekly.

Your OB will perform routine tests along the way, with the group B strep test—also known as the GBS—being one of the final ones. It’s performed on every woman and it requires a vaginal exam in which a nurse takes a test swab.

The American Pregnancy Association tells us that group B streptococcus is a type of bacterial infection that can be found in a pregnant woman’s vagina or rectum.

“This bacteria is normally found in the vagina and/or rectum of about 25 percent of all healthy, adult women,” according to the association. “Women who test positive for (group B strep) are said to be colonized.”

Group B strep is a normal bacteria that healthy women can have. A mom doesn’t know if she’s negative or positive and she won’t have any symptoms. (Interestingly, men also carry group B strep.)

The CDC estimates 1 in 4 women are carriers. The strange thing is you can be negative early in pregnancy, but then positive at testing time. This is why the test is typically done at about 35-37 weeks into the pregnancy.

The test is most accurate within five weeks of delivery.

The concern surrounding group B strep is not for the mom but for the baby. If the mom is positive for group B, it can be passed to the baby during the delivery process.

And yet, not all babies will become sick if their mom has the bacteria.

What improves a baby’s odds of remaining healthy? An antibiotic treatment for the mom—administered during labor, before delivery.

Studies show that about 1 in 200 babies will develop signs of group B strep if the mom has the bacteria and she has not received an antibiotic in labor, according to the American Pregnancy Association.

On the other hand, if a mom has group B strep and she takes the antibiotics in labor, the baby’s chances of getting the bacteria are 1 in 4,000.

So what happens if you are positive for group B strep? Your provider would want to give you an antibiotic while you are in labor, before the baby is born.

Why can’t a mom take the antibiotics before labor begins? You could be positive for group B strep even after the antibiotic is completed, which makes labor the better time.

You may be wondering how bad this bacteria is if baby acquires it from mom. In the U.S., it is the leading cause of sepsis and meningitis. It can also cause breathing problems, heart issues, kidney problems and more.

It is definitely something you don’t want your baby to deal with after birth. Babies with group B strep can get sick very quickly and be quite sick.

And we know that the best way to prevent it is to provide mom with antibiotics in labor.

So there you have it: When you have your group B strep test done, you’ll know what it’s for and how important it is.