GBS in Pregnancy: Can I Prevent a Positive Result?

GBS in Pregnancy: Can I Prevent a Positive Result?

What is GBS?

Group B Streptococcus (GBS) is a strain of bacteria that can be found in anywhere from 10-35% of pregnant women at any given time— in fact most people go through phases of “colonization” by GBS with no symptoms and no ill effects at several points in their lives. The bacteria lives in the intestines and can be found in the vaginal/rectal area as well as urinary tract when active.

GBS rarely poses the threat of infection to an adult woman; however, it can cause infections such as pneumonia, meningitis, and sepsis in infants if transferred to them during birth. As baby passes through the vagina he can accumulate and later ingest the bacteria; baby can also be at risk if she ingests bacteria that has made its way to the amniotic fluid after your waters have broken.

How Will I Know If I Have It?

Both OBs and midwives will offer a routine swab for GBS between your 35th and 37th weeks of pregnancy. The reason for this particular window of timing is so that it is more likely to be accurate at the time of delivery, in order to avoid administering antibiotics when not needed, or not administering them when they are needed.

The GBS swab may be considered an optional test by your health care provider. If you choose to decline the test, at some hospitals the policy is to assume a positive result when there is no known result, and you may be administered antibiotics as a precautionary measure. If you are birthing at home and have declined GBS testing, no antibiotics will be administered.

What If I Test Positive?

If you test positive for GBS colonization at the end of your pregnancy, administering antibiotics will be added to your birth plan. This means that when you go into labour, you will be administered medication via an IV— as much as possible four hours before you deliver your baby. The antibiotics can be re-administered every four hours until you give birth.

If antibiotics are the only thing you are being given via IV (ie. you are not receiving fluids, an epidural, or other medications), they only take about 15-30 minutes to administer, so there is minimal effect on your mobility during labour or ability to use comfort measures such as the shower, birth pool or tub, or movement.

A GBS positive result also has no effect on your choice of birth place— the IV can be given at home, at the clinic, or in a hospital setting.

Is My Baby at Risk?

Research shows that babies born to GBS-positive mothers who are not treated with antibiotics in labour have a 50% risk of being colonized by the bacteria, and a 1-2% risk of contracting a serious illness because of it. Research also shows that risk decreases by 80% for babies born to GBS-positive mothers who are treated with antibiotics during labour, leaving only 0.2% chance they will develop an infection.

How Can I Minimize Chances of a Positive GBS Swab?

During pregnancy there are a few things you can do to try to promote the growth of healthy bacteria in your body, and minimize your chances of testing positive for GBS prior to delivery.

Limit sugar intake: sugar feeds bacterial growth; for this and many other reasons it is ideal to limit your sugar intake during pregnancy and for optimal health lifelong.

Take a probiotic supplement or eat probiotic-rich foods like yogurt or fermented foods to boost healthy gut bacteria.

Drink lemon water daily to help maintain a healthy vaginal pH level and help prevent UTIs.

Consume garlic or take a garlic supplement; garlic is known to be antibiotic and may prevent growth of harmful bacteria.

Rest and sleep regularly to avoid stressing your body.

Exercise to stimulate your immune system.


Ontario Midwives
Evidence Based Birth
Natural Birth and Baby Care
Benefits of Lemon Water



  1. Marissa Bolanos August 3, 2017 at 12:58 pm - Reply

    Thanks for this awesome information. I ambiguously knew that probiotics could help prevent GBS but I couldn’t remember exactly why. I drank kombucha and ate sauerkraut every day for two weeks before the test and it came out negative, so I guess it worked 😉

    • Margaret Flietstra August 8, 2017 at 8:06 pm - Reply

      I was drinking (and brewing) kombucha daily before becoming pregnant… I stopped during the first trimester because of ambiguity in the research on safety and the fact that I was home brewing. But I’m seriously considering starting up again now that I’m at 30 weeks… I know there are so many benefits not the least of which being the probiotic value!

  2. Ashley August 3, 2017 at 7:33 pm - Reply

    This is such good advice. I tested positive and really wished that I had done more to try and prevent it, but I naively did the test thinking “I’ll be negative for sure” – live and learn!

    • Margaret Flietstra August 8, 2017 at 8:04 pm - Reply

      Next time! Did the positive result have any negative impact on your birth experience?

  3. Giovanna Aiello August 3, 2017 at 8:45 pm - Reply

    Very informative! Thank you for sharing this…I drank lemon water every day while I was pregnant, I had no idea that it probably helped me pass the GBS test!

    • Margaret Flietstra August 8, 2017 at 8:03 pm - Reply

      I bet it did! What were your other reasons for drinking lemon water?

  4. Toni Botas August 4, 2017 at 9:54 am - Reply

    This is AWESOME! Evidence backed information on what Group-B Strep is and what happens when a woman has it. I have had several clients who tested positive in several pregnancies, and decided to take a high quality probiotic with their subsequent pregnancy and tested negative, so I think there is something to say for probiotics and good vaginal bacteria levels! This is an easy-to-read article for parents who have questions about GBS. Thank you!

    • Margaret Flietstra August 8, 2017 at 8:03 pm - Reply

      Thank you Toni! Will definitely be a topic I add to my prenatals as it’s just much better to avoid the extra hassle that a GBS+ swab brings. Seems like probiotics are the go-to remedy based on anecdotal evidence too.

  5. […] The third trimester is a great time to start taking probiotics, and as I have not been taking them regularly already, I’ll be sure to start by the time I reach 32 weeks. Probiotics help build healthy gut bacteria that can be beneficial in helping avoid a positive GBS swab. […]

  6. Rhondda Smiley August 29, 2017 at 1:29 am - Reply

    Taking those probiotics can also help reduce a mom’s risk for developing thrush (a yeast overgrowth in the breast) once baby is here. I went through about 7 or 8 different treatments for excruciatingly painful thrush, both natural and medicinal, and it was massive doses of probiotics that finally killed off the “yeasty beastie”! If I’d taken them during my pregnancy, it might have been a non-issue.

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