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In this bonus episode, we wrap up our 2-part series on Group B Strep in Pregnancy, where I answer some of your questions following the first two episodes.

Here are the questions answered in this bonus episode:

  1. Is it possible to retest between an initial GBS swab and going into labor? Are there things that can be done to get a negative test before labor occurs?
  2. If you are GBS positive in one pregnancy, are you likely to be positive in subsequent pregnancies?
  3. Discussion about an important limitation to one of the studies in our GBS update.
  4. Discussion about risk factors and the “Other Risk Factor” approach vs the Universal Screening approach
  5. Is there evidence for screening for GBS twice in the same pregnancy?

Make sure you listen to Part 1 and Part 2  to review the updated GBS research.

Resources and References


  • Listen to EBB 254: Group B Strep in Pregnancy Part 1 here
  • Listen to EBB 257: Group B Strep in Pregnancy Part 2 here
  • Listen EBB 87: Cristen Pascucci on How to Disagree on Birth Topics Respectfully! here
  • Learn more about the use of antibiotics in labor in our Pocket Guide to Labor Interventions 


  • Parente V, Clark RH, Ku L, Fennell C, Johnson M, Morris E, Romaine A, Utin U, Benjamin DK, Messina JA, Smith PB, Greenberg RG. Risk factors for group B streptococcal disease in neonates of mothers with negative antenatal testing. J Perinatol. 2017 Feb;37(2):157-161. doi: 10.1038/jp.2016.201. Epub 2016 Nov 17. PMID: 27853322; PMCID: PMC5280520.
  • Kabiri D, Hants Y, Yarkoni TR, Shaulof E, Friedman SE, Paltiel O, Nir-Paz R, Aljamal WE, Ezra Y. Antepartum Membrane Stripping in GBS Carriers, Is It Safe? (The STRIP-G Study). PLoS One. 2015 Dec 31;10(12):e0145905. doi: 10.1371/journal.pone.0145905. PMID: 26719985; PMCID: PMC4697801.




Rebecca Dekker:

Hi everyone. On today’s podcast, I’m going to do a mini Q and A about Group B Strep.

Welcome to the Evidence Based Birth® podcast. My name is Rebecca Decker and I’m a nurse with my PhD. I’m the founder of Evidence Based Birth®. Join me each week as we work together to get evidence based information into the hands of families and professionals around the world. As a reminder, this information is not medical advice. See for more details.

Hi everyone, and welcome to today’s episode of the Evidence Based Birth® podcast. My name is Dr. Rebecca Dekker, pronouns she, her and I’ll be your teacher for today’s episode. Today I’m so excited to answer some of your questions that you’ve been submitting about Group B Strep during pregnancy. Before I get started, I have an important announcement for you. We are having a free public webinar all about some of the latest evidence on water birth prom or premature rupture of membranes and Group B Strep where we’re going to review the updated evidence and debunk some myths about each of these topics. We’ll have two identical showings of this webinar. The first is Thursday, April 20th, and the second is Sunday, April 23rd. If you cannot attend live, go ahead and sign up anyways because we’ll send you the link to the replay afterwards and we only have these free public webinars twice a year, so don’t miss your chance to engage with me, the research team at Evidence Based Birth® and the rest of our community.

Now, today is the third time on the EBB podcast that we’re focusing on Group B Strep and we’re doing this to celebrate our update on the signature article on the evidence on Group B Strep in Pregnancy, which is available on our website at In part one of our podcast series on Group B Strep, episode 254, I talked about the evidence on GBS during pregnancy, how the microbiome works in the body, the evidence on getting tested for GBS and the evidence for antibiotics, including the pros and cons of having antibiotics during labor for GBS, as well as options for people who are allergic to penicillin. In part two, I went on to discuss the evidence on alternative treatments for GBS and answered a few of your questions about GBS. And today, in part three I’m going to do a mini Q and A and answer a few of your questions that were asked on social media or sent to us by email.

And this is something new we’re going to try, where on months where there are five Wednesdays in a month. On the fifth Wednesday we’ll do a short Q and A or a mini question and answer session. Before we get started, I want to remind you that we know GBS is a controversial subject, and some people get really upset when we talk about testing for GBS or taking antibiotics to prevent GBS disease. So please, don’t lash out at me or our team here at EBB or in our email inbox or on social media. Our role here is to provide you with the information we’ve been gathering, not judgment. Please try to separate this information from your emotional response. You can learn more at EBB 87 How to Disagree on Birth Topics Respectfully. If you have a question that is still not answered after all three podcast episodes on Group B Strep, the only place we can directly answer questions about the research is inside the Ask the Research forum inside the EBB Pro membership, which you can join by going to

We do have a free one page handout on the evidence on GBS that you can download from our website to use and informed decision making discussions. It’s available in English and Spanish, just go to to access the entire full text of our article on Group B Strep, all the scientific references and the free one-page handout.

Are you ready to get started with our mini Q and A? All right, let’s go.


Our first question is, are there any data on retesting between the initial swab for GBS and then later when you go into labor? Is there anything I can do if I get a positive test at 36 weeks, could I try and get a negative test before labor occurs? So, here’s my answer.

If you test positive at any point in pregnancy, that means you are a GBS carrier. This means that it is a normal or physiological part of your microbiome. Even if you try to improve your microbiomes that the GBS is no longer present in your vagina or rectum later on, it’s still present in your gut. You cannot eliminate it entirely. You can only suppress it temporarily.

So, it is possible to try to retest later in pregnancy. Your insurance might not cover. It might be something you have to pay for yourself. And it’s possible that you could suppress GBS and avoid having GBS physically present in your birth canal during labor, but most providers are going to consider that since you’ve tested positive once, they will consider you a carrier and will recommend that you have antibiotics during labor. That’s a conversation you’d have to have with your provider and it probably would not be an easy one. Of course, it is your body and you have the right to accept or decline antibiotics. Nobody can force you to do anything. And we cover the topic of informed consent and refusal in our EBB childbirth class and on our pocket guide to interventions.

This next question is related. The question is, if you’re GBS positive in one pregnancy, are you likely to be positive in a subsequent pregnancy? And this commenter said, “I had GBS in my urine during a routine lab check in my second pregnancy and was not swabbed late in pregnancy because my care team said it’s already there. So they would plan to do IV antibiotics during delivery, which I was fine with at the time, but I was annoyed with it during labor. I was induced and I swore they prolonged the induction because they wanted to get a certain number of antibiotic doses in. I’m interested to see if my risk for having GBS in another pregnancy goes up since I’ve had it once before. I didn’t have it in my first pregnancy though.”

So it looks like this person tested negative in their first pregnancy, had it in their second pregnancy where they tested positive with a urine culture and they’re wondering about their third pregnancy. What are their chances of having GBS?

Interestingly, someone commented beneath this person on social media and gave an incorrect answer, which unfortunately is common where if you just ask the random public sometimes they will give you incorrect answers. The incorrect answer was “GBS is a bacteria we all have in our system. Sometimes it shows up and sometimes it doesn’t.” That is incorrect because GBS is not something that everyone has in their system. About 18% of pregnant people around the world are GBS carriers and have GBS as a normal part of their microbiome. That percentage can be lower, but it can also be as high as 33% in some geographic areas. Some people will never test positive, they’ll always test negative, and that’s because GBS is not a part of their microbiome. Some people, every time they test, they test positive. For other people, they may test positive with one pregnancy or negative with the next pregnancy or vice versa.

So why does some people’s results change? Well, what this means is that if you carry GBS as a normal or physiological part of your microbiome, then it is present in your intestines. It’s just part of your ecosystem. And when it grows in heavier amounts, when it’s flourishing, it can migrate down to your rectum and then sometimes spread to the vagina and then it would be in your birth canal. Researchers believe that the healthier your microbiome and the more probiotics you have such as lactobacillus, the more acidic your vagina environment is and the less likely GBS is to populate your vagina because GBS does not thrive in highly acidic areas. And this is why some researchers have been testing, giving probiotics during pregnancy to see if that can lower your chance of testing positive. Unfortunately, the research up through 2022 was not very high quality and the only high quality randomized trial on giving probiotics during pregnancy for this purpose did not find evidence that it’s effective to give probiotics to suppress GBS and make you test negative.

And that leads me to my next question, and it’s a comment from one of the authors on that study that I was just talking about. One of the authors on the Hanson Et. Al 2022 and 2023 studies reached out to EBB thanking us for our work and wanted to reach out about a couple of points that we mentioned in our article on GBS. One of the points they wanted to make is that in their randomized trial, which was published in 2023 on giving probiotics to try and help people test negative for GBS, did not find a difference between the probiotic group and the placebo group. And they say that this is because their study was not powered to find a difference. Originally, they thought it would be, but they did their original statistical calculations assuming that at least 30% of people in their study would have GBS, based on that the rate that they’d seen the year before.

However, when they actually did the study, the prevalence of GBS in their population was more like 20%. So, they didn’t have enough GBS carriers in their study. And this is an important limitation and it just means that we would need more people in a study to find a difference. If you had fewer people with GBS, it just makes sense you’d need a larger study to look at seeing if giving probiotics would suppress the GBS. I think this author is totally right. A larger trial would be helpful and another trial where people are more adherent to taking the probiotics because in the study where they didn’t find a difference between the probiotic group and the placebo group, they were only about 51 to 60% adherent, meaning they missed taking the probiotics 40 to 50% of days.

Also, someone else recently pointed out to me that if you treat the birthing person with probiotics but not their partner, if they have one, it might not make as much of a difference to treat the birthing person because the partner might continue to interact with them in a very close contact way, could pass GBS between one another. And we talk a little bit about that in our article on GBS, just how the microbiome works and how close contact with people may change the intricacies of your microbiome. The author was also curious about why we included membrane stripping as a risk factor for early onset GBS disease in newborns. There was one study that found an association, but they pointed out another study where an association was not found between membrane stripping and GBS disease and newborns. So my guess is that membrane stripping may or may not be a risk factor. We don’t have solid evidence on that yet, but it’s probably only a risk factor if you had unintended rupture of the membranes occur.

For example, one randomized trial on membrane stripping found that about 10% of the time when you have membrane stripping, it unintentionally breaks your water and so it would make sense that that could be a risk factor for early GBS disease because that might lead to extended length of time after your water is broken, before your baby is born.

Another midwife wrote in and said “I think it’s important that readers understand what the risk factors are. The risk of GBS disease in newborns goes up significantly if someone tests positive with universal screening and develops a fever in labor or has their water broken for 18 or more hours.” We do cover these other risk factors in detail in our article at Although it’s true that the risk of GBS disease in newborns goes up if the birthing person is a GBS carrier, plus they have another risk factor. About 60% of babies who develop early GBS disease had none of the other risk factors, and their only risk factor is that the birthing person was a carrier of GBS.

So, if you’re with a practice that has a policy of only treating people with antibiotics if they are GBS positive plus they have one other risk factor, that is obviously a choice that parents can make. But part of the informed consent process should be to let them know that 60% of babies with GBS disease, early onset disease, have no other risk factors other than their parent being a GBS carrier. And I believe the Association of Ontario Midwives has a really good document that you can use to help with informed consent that covers all of the options and alternatives, including the option to use what we call a combination approach where they’re combining universal screening with other risk factors. And unfortunately, we don’t have research yet showing whether or not that approach is effective.

Finally, I have one more question and that question is, “my care provider says I need to be tested for GBS twice, once in early pregnancy and once more at 36 weeks. Is this evidence based?” This question was fascinating to me because I have never heard this before. This question was submitted to me, and so we included it in our article on GBS. I have never seen anything published about this in the clinical guidelines or in the research. My guess is maybe care providers are testing their clients early to get an idea if you’re GBS positive, just so they know in advance. But GBS is the cause of only about one to 2% of preterm birth. So it doesn’t make sense that you’d be using it as screening for preterm birth risk.

And my other thought is maybe they found it in a routine urine culture. So they’re often doing a screening to make sure in the first trimester that you don’t have a UTI, and if they find a UTI, they would then look to see what is causing the UTI. If they find that Group B Strep is the cause of the UTI, then you’re considered to be positive for Group B Strep because that’s a sign that you’re a heavy carrier, you have a lot of GBS in your microbiome. In that case, UTIs do need to be treated, and you want to try and eliminate the GBS from your urinary tract because it’s not normal to have it in your urinary tract, although it is normal part of people’s bodies to have it in their intestines.

So I hope you enjoyed this mini Q and A on some of the questions we’ve gotten about Group B Strep and our discussion about how it’s a part of your microbiome, how it can be present in higher amounts, be present in lower amounts, never present at all, and just all the different options out there. Don’t forget that you can access all the research and everything we’ve written about GBS and the alternatives to antibiotics. You can get it all for free at, along with a one page handout that you can download to help guide discussions with care providers and clients.

I hope you enjoyed this little mini Q and A. See you all next week. Bye.

Today’s podcast was brought to you by the signature articles at Evidence Based Birth®®. Did you know that we have more than 20 peer reviewed articles summarizing the evidence on childbirth topics available for free at It takes six to nine months on average for our research team to write an article from start to finish, and we then make those articles freely available to the public on our blog. Check out our topics ranging from advanced maternal age to circumcision, due dates, big babies, Pitocin, vitamin K, and more. Our mission is to get research evidence on childbirth into the hands of families and communities around the world. Just go to, click on blog, and click on the filter to look at just the EBB signature articles.


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