Group B Strep Test

What Every Mom Needs to Know Before 36 Weeks

At some point between your 35- and 37-week checkups, your provider is going to mention something that probably wasn't on your radar yet: the Group B Streptococcus (GBS) test. It's not one of the big, flashy moments like your 20-week anatomy scan or your glucose screening drama. But it is a super important step in making sure you and baby are safe during delivery—especially since Group B Strep is something many pregnant women carry without even knowing it.

So, what is this test? Why does it matter? And what happens if you test positive? If you're feeling even a little nervous or unsure about what to expect, this blog is for you. I'm going to walk you through what GBS is, how the test is done, what a positive result really means, and how to feel prepared—not panicked—heading into this appointment. Think of this as your straightforward, no-shame guide to navigating one more box on your prenatal checklist with confidence.

So, What Is Group B Strep?

Group B Streptococcus is a type of bacteria that lives in the bodies of about 25% of healthy adult women—specifically in the vaginal or rectal area. It's not sexually transmitted, and it usually doesn't cause symptoms or problems for the person carrying it. Most people never even know they have it unless they're tested.

But here's the deal: during labor and delivery, GBS can be passed to your baby as they move through the birth canal. And while most babies exposed to GBS are completely fine, there's a small risk (think less than 1%) of serious complications like sepsis, pneumonia, or meningitis. That's why it's part of routine prenatal care to screen for it late in pregnancy—so your care team can act early and prevent those risks.

The Test: Here's What to Expect

You'll usually be tested sometime between 36 and 37 weeks, although some providers bring it up a little earlier or later depending on your situation. The test itself is fast and simple: a quick vaginal and rectal swab that takes less than 15 seconds. No speculum, no pain—just a swab, usually done during your regular prenatal appointment. Some practices will even offer you the option to self-swab in private (definitely worth asking about if that makes you more comfortable).

The swab is then sent to a lab, and you'll typically get results back within 1 to 3 days. If you're GBS-negative, congrats! No further steps needed. If you're GBS-positive, your provider will recommend a plan to give you IV antibiotics during labor, typically starting as soon as your water breaks or when active labor begins.

Okay... So What Happens If I Test Positive?

Deep breath—this is common, manageable, and doesn't mean anything is wrong with you or your baby. Around 1 in 4 pregnant people test positive for GBS. The bacteria comes and goes naturally in the body, so it's not about hygiene, habits, or anything you "did wrong."

Here's what happens if you're GBS-positive:

• During labor, you'll receive IV antibiotics, usually penicillin, every 4 hours to reduce the chance of transmitting GBS to your baby.
• If you're allergic to penicillin, your provider will choose an alternative based on your allergy profile.
• Antibiotics are only given during labor, not during pregnancy—so don't expect a prescription to go home with.
• Most birth plans can stay exactly the same. You can still labor in the tub, move around, use your birth ball, etc. unless other complications are present.

And yes, GBS-positive moms can still deliver vaginally, have skin-to-skin contact, and breastfeed right away if everything else is smooth.

Chloe's GBS Prep Checklist 📝

You know I love a good list. If you want to feel 10 steps ahead before your appointment, here's what I recommend:

Before the Test:

• Ask your provider when they plan to test (aim for the 36–37 week mark)
• Confirm if self-swabbing is an option
• Speak up about any allergies to penicillin or other antibiotics

If You Test Positive:

• Understand when to head to the hospital (usually sooner after water breaks if you're GBS+)
• Pack extra snacks and comfort items—you might be there a little longer due to IV timing
• Bring your birth preferences, and discuss how GBS treatment fits into your plan

If You Had GBS in a Past Pregnancy:

• Ask your provider whether they'll automatically treat you in labor, even without retesting

Final Thoughts

The Group B Strep test is one of those third-trimester things that doesn't get a ton of attention—but it's an important one. If you test positive, you're in good company, and your care team has protocols in place to protect your baby with minimal disruption to your birth plans. If you test negative, awesome—you're one step closer to delivery day with one less thing to think about.

Either way, remember this: you're not failing a test if you're GBS-positive. You're gathering information that helps your provider take the best care of you and your baby. That's proactive. That's empowered. That's smart mom energy.

One simple test, one clear plan, one less thing to worry about.

Got a mom friend coming up on her 36-week mark? Send this her way so she's in the know too.

Want a printable version of this checklist or a short explainer to save on your phone? I can whip that up too—just ask! 💡