When preparing for birth, one routine step you may hear about is the group B strep test. This test is an important part of prenatal care, designed to protect both you and your baby during labor and delivery.
Why the Group B Strep Test Is Done
Group B streptococcus (GBS) is a type of bacteria that can naturally live in the digestive tract or vaginal area. For most adults, it’s harmless and doesn’t cause symptoms. However, during childbirth, GBS can be passed to the baby, sometimes leading to serious infections such as pneumonia, sepsis, or meningitis. The group B strep test helps identify who carries the bacteria so that preventive steps can be taken.
When the Test Happens
The group B strep test is typically done between 35 and 37 weeks of pregnancy. The test itself is quick and simple. A swab is gently taken from the vagina and rectum and sent to a lab for results. It’s not painful, and it gives providers the information they need to plan ahead for your delivery.
What Happens if You Test Positive
Testing positive for GBS does not mean you are sick or have done anything wrong, it simply means the bacteria is present. The standard care is to receive IV antibiotics during labor. This significantly reduces the chance of passing GBS to your baby. The medication is only given while you’re in labor, so it doesn’t affect your pregnancy beforehand.
Who’s at Higher Risk for GBS Complications
GBS is common, and most people who carry it have completely healthy deliveries once they receive antibiotics in labor. A few factors raise the risk of it affecting your baby, which is why providers pay close attention to:
- A previous baby who had a GBS infection
- GBS detected in your urine at any point during this pregnancy
- Labor or rupture of membranes before 37 weeks
- Your water breaking 18 or more hours before delivery
- A fever during labor
If Labor Starts Before You’re Tested
Not every birth follows the 35 to 37 week testing window. If your water breaks or labor begins before you’ve been tested, or before results are back, your provider will usually treat you as though you’re GBS positive and start antibiotics as a precaution. If you’re not sure what your water breaking should look or feel like, our guide on what to do if your water breaks covers what’s normal and when to call your provider.
Can You Decline the Test or the Antibiotics?
Yes. Like any part of prenatal care, GBS testing and treatment are your choice, and a good provider will walk you through the risks and benefits either way rather than just handing you a form. If you’re weighing whether to decline a test or a recommended treatment, it helps to understand what informed consent actually looks like in maternity care. See our guide to consent in maternity care for the questions worth asking.
Final Thoughts
The group B strep test is a routine part of prenatal care that helps keep babies safe after birth. If you test positive, know that effective treatment is available and widely used.
If you’re preparing for birth and want to know what to expect once you’re home, Doulas of Utah provides daytime and overnight postpartum support so you’re not navigating recovery and newborn care alone. Learn how our postpartum doulas can help.
Group B Strep: Your Questions Answered
No. It’s a simple swab of the vagina and rectum, and most people say it feels like mild pressure at most. It takes under a minute, and in some practices you can even do the swab yourself.
The antibiotics work best when given at least 4 hours before delivery, so your care team starts them as soon as labor begins if you’re GBS positive. If your baby arrives faster than that, they’ll simply be watched more closely after birth for early signs of infection, like trouble breathing or feeding, rather than treated automatically.
Usually not, if your water hasn’t broken and labor hasn’t started before the surgery. GBS is passed to the baby through the birth canal, so a C-section done before labor begins carries a much lower risk. Confirm this with your provider, since it can depend on your specific situation.
It’s uncommon when antibiotics are given during labor, but it’s worth knowing the signs: fever, trouble breathing, feeding poorly, or unusual fussiness or lethargy in the first week. Mention your GBS status to your baby’s pediatrician so they know to watch for it.
