Group B Strep In Pregnancy - Part 2: What To Do If You Test Positive


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In the first part of this series on Group B Strep in pregnancy, we covered what GBS is and what it means for mom and baby. We learned that it may be a good idea to be aware of GBS in your first trimester, rather than your third.

As it turns out, if you plan ahead of time, you can reduce the  risk of being colonized by GBS and create an action plan if you do have it.

In this second part of the series we’ll learn about the standard antibiotic treatment for GBS, alternative ways that may help you get rid of GBS before you’re offered antibiotics, and ways to restore your baby’s gut microbiome if you end up having antibiotic treatment during labor.

The standard GBS treatment 

Antibiotic treatment during labor is the standard method to protect your baby against early-onset GBS infection [1], [2]. You will most likely be prescribed antibiotics during labor if: 

  • You got a positive GBS pregnancy test
  • Your previous baby had a GBS infection, even if now you have a negative GBS test 
  • You tested positive for GBS in your urine earlier during pregnancy
  • You go into preterm labor (before 37 weeks)
  • You have preterm rupture of the membranes or prolonged rupture of membranes for 18 hours or longer and the result of your GBS test is unknown.
  • You have high fever during labor (temperature 100.4°F [38°C] or higher) and your GBS test result is unknown

Beginning antibiotics 4 hours before birth is considered to be effective in preventing the transmission of GBS to the baby. As it turns out, the risk of your baby developing early onset GBS infection decreases by more than 80% from 0.5% to 0.025% if you are treated with antibiotics during labor [1], [2].

Commonly prescribed antibiotics for a positive GBS pregnancy test include: 

  • Intravenous penicillin, administered every 4 hours during labor until delivery. 
  • Ampicillin is an alternative to penicillin, also administered every 4 hours during labor until delivery.
  • Clindamycin for women allergic to penicillin, every 8 hours during labor until delivery. 
  • Intravenous vancomycin in women with penicillin allergy and GBS not sensitive to clindamycin, administered every 12 hours until delivery [2].

Do antibiotics during labor impact my baby’s gut microbiome?

Although antibiotics reduce the risk of GBS infection in a baby, they can also affect a baby’s microbiome both short and long term.

Babies born to moms who received antibiotics during labor may have:

  • Less diverse gut microbiome
  • Higher levels of disruptive bacteria such as Enterobacteriaceae and Proteobacteria
  • Reduced beneficial bacteria such as Bifidobacterium, Bacteroidetes, and Actinobacteria [3]–[5]

It’s possible that if such a disruption in the early baby gut microbiome is not corrected, this may lead to health concerns later in life, such as asthma, allergies, obesity, and diabetes.  

For example, one study found an association between the use of group B Strep antibiotics during labor and higher BMI (body mass index) during childhood [6].

But the good news is that you can help to restore your baby’s microbiome with exclusive breastfeeding for at least 3 months, or as long as possible. You can also supplement your baby with beneficial probiotic bacteria designed specifically for babies.

It is important to note that if antibiotics are used less than 24 hours during labor, the effect on the baby’s gut microbiome is mostly short-term and can be reversed by breastfeeding.

For example, one study found that exposure to antibiotics for less than 24 hours was not associated with the development of eczema in babies born vaginally [7]. In another study, antibiotic use for GBS for more than 4 hours before birth was not associated with the development of asthma, eczema, or food allergies in babies born vaginally [8].

Can I decline antibiotics during labor?

If you plan a hospital birth, you have the right to refuse medical treatment, including antibiotic treatment. The informed right to refuse medical treatment is codified in the ACOG Refusal of Medically Recommended Treatment During Pregnancy. You can also refer to the Patient Rights and Responsibility Act of 1990.

Keep in mind that if you plan a homebirth, midwives usually don't administer IV antibiotics.

Alternative GBS protocols: do they work? 

There are some alternative options that may help you keep GBS colonization in check.


Studies are contradictory, but some probiotic strains, such as the combination of Lactobacillus rhamnosus GR1 and Lactobacillus reuteri RC-14 have been shown to be effective against GBS in some people. These probiotic strains may help reduce vaginal and rectal GBS colonization [9], [10]. Always remember that the probiotic effect is strain-specific.


Garlic contains allicin, a compound with strong antimicrobial properties against some disruptive microbes such as GBS [11], [12]. 

Some midwives recommend increasing the consumption of garlic as a more traditional way to fight GBS infection. Another recommendation is to insert a freshly cut garlic clove into the vagina (2 to 3 inches in) at bedtime and remove it in the morning, for 3-6 weeks, which can also help with long-term GBS infections in non-pregnant people [13].

However, there aren’t any clinical studies demonstrating the positive effects of garlic in GBS-positive pregnant or non-pregnant women, either through oral intake or vaginal insertion. Since garlic has antimicrobial properties against a wide variety of microbes, it may also disrupt your beneficial vaginal microbiome. We just don’t know. 

So while increasing oral consumption of garlic - and particularly raw garlic - is always a good thing for your overall gut and vaginal health, less is known about the net benefits of using garlic as a vaginal suppository. 

Essential oils

Another often recommended alternative treatment for GBS is the use of essential oils. Essential oils have been laboratory-tested and shown to have antimicrobial properties against many disruptive bacteria, including GBS [14], [15]. Essential oils can be used in the form of vaginal suppositories, available on the market or homemade to help you fight GBS colonization. 

But similar to garlic, there aren’t any clinical studies showing the effects of essential oils for GBS-positive pregnant or non-pregnant women. We also don’t know how essential oils affect your vaginal microbiome. Always ask your provider before trying these. 

If you’re wondering which products or methods might be best for you, Dr. Aviva Romm shares her go-to homemade suppository essential oil blend for addressing GBS colonization or infection.

I was given antibiotics during labor. What can I do to restore my baby’s microbiome?


As it turns out, breastmilk can do wonders for your baby’s gut microbiome. By 30 days of age, exclusively breastfed babies that were exposed to antibiotics for GBS, have more Lactobacillus and Bifidobacterium species [5]. By one year of age, your baby’s gut microbiome can potentially recover from the antibiotic use at birth, especially if the baby was breastfed for at least 3 months [16].

Use baby probiotics

Bifidobacterium can help restore your baby’s gut microbiome after antibiotic use. It’s important to note that not all probiotics are created equal. You want to choose a product with probiotic strains that can colonize a baby’s gut for it to work effectively.

If possible, we recommend that you use probiotics in combination with breastfeeding because the HMOs in breastmilk can feed the probiotic microbes and help them grow more effectively. 

It’s important to note that we don’t recommend using a baby probiotic if your baby already has adequate levels of Bifidobacterium.

A few last words about testing positive for Group B Strep in pregnancy  

When you test positive for GBS, it’s important to make choices that feel good for you and your baby. Choose what makes you feel safe. 

For some parents, a 0.001% mortality risk from GBS infection is so low, that they may opt for no antibiotic use. Other parents may want the peace of mind that comes with reducing any chance of early-onset GBS infection.

If you are given antibiotics during labor, breastfeeding for at least 12 weeks can help  to reverse the effects of antibiotic use.

That said, testing your vaginal microbiome and your gut microbiome in your first trimester can prepare you to take action early on, months before your third trimester GBS screening. Depending on where you’re at, whether pregnant or postpartum, this may or may not be an option. 

Regardless, go easy on yourself. Breastfeed if possible. Get support where you can. And trust that you know what’s best for you and your family.

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