Understanding GBS: What You Need to Know About Group B Strep in Pregnancy
Pregnancy comes with countless tests and terms that can feel overwhelming. One of those terms you might hear is Group B Streptococcus (GBS). If you’ve never heard of it before, you’re not alone—but it’s something that’s important to understand during pregnancy.
In this post, we’ll break down what GBS is, the risks it poses, treatment options, and the benefits and risks of the treatment. We also look at what standard care looks like in countries like Canada, the USA, the UK, and Australia to help guide you in making an informed decision about your care during pregnancy and birth.
What is GBS?
Group B Streptococcus (GBS) is a type of bacteria that naturally lives in the intestines, rectum, and vagina of about 20-30% of healthy adults. It’s considered part of the body’s normal flora, meaning it usually causes no harm to those carrying it.
However, during pregnancy, GBS can pose risks if passed to the baby during birth, which is why it’s routinely screened for and managed in many countries.
What Causes GBS?
GBS bacteria are not sexually transmitted, nor are they caused by poor hygiene. It’s simply a naturally occurring bacteria in the body that some individuals carry and others do not. It can come and go over time, so testing positive at one point doesn’t mean you’ll always have it. You may test positive but be negative by the time you go into labor.
Screening and Standard Practice in Canada, USA, UK, and Australia
Each country has slightly different approaches to GBS screening and treatment. Here’s a brief overview:
Canada & USA:
Routine GBS screening is performed between 35-37 weeks of pregnancy using a swab of the vagina and rectum.
If a woman tests positive for GBS, she is offered IV antibiotics during labor to prevent transmission to the baby.
Antibiotics are not typically given before labor because the bacteria can regrow.
UK:
The UK does not routinely screen all pregnant women for GBS. Instead, they use a risk-based approach.
Women are offered antibiotics in labor if they have risk factors, such as:
A previous baby with GBS infection
GBS found in the urine or vaginal swabs during pregnancy
Preterm labor (before 37 weeks)
Prolonged rupture of membranes (waters breaking for more than 18 hours)
Fever during labor
Australia:
Like Canada and the USA, GBS screening is offered to all pregnant women between 35-37 weeks.
Women who test positive are given IV antibiotics during labor to reduce the risk of transmission.
If a mom tests positive for Group B Strep (GBS), the chances of her baby developing a GBS infection are very low overall, but let’s break it down into simple numbers so it’s clear:
1. How likely is it that a baby will get a GBS infection?
About 1 in 200 babies (0.5%) born to GBS-positive moms who do NOT receive antibiotics during labor will develop a GBS infection.
To flip that around: 199 out of 200 babies born to GBS-positive moms without antibiotics will NOT get infected.
If antibiotics are given during labor, the risk drops even further:
About 1 in 4,000 babies (0.025%) will develop a GBS infection when mom receives antibiotics.
2. How serious is a GBS infection if it happens?
If a baby develops a GBS infection, it can be serious because it can lead to conditions like:
Sepsis (a blood infection)
Pneumonia (a lung infection)
Meningitis (infection of the brain lining).
Roughly 5-10% of babies with GBS infection will face long-term complications, like developmental delays, hearing loss, or neurological issues, depending on how severe the infection was.
3. How likely is it that GBS infection will cause death?
If a baby develops a GBS infection, about 2-3% of these cases may result in death.
Put another way: 97-98% of babies who develop a GBS infection will survive.
To summarize with simple numbers:
If mom is GBS-positive and receives no antibiotics, there’s a 0.5% chance (1 in 200) the baby will get infected.
With antibiotics, the chance drops to 0.025% (1 in 4,000).
Of the small number of babies who do get infected:
90-95% recover fully.
Around 5-10% may have long-term health issues.
2-3% of infected babies may not survive.
97-98% are expected to survive.
To compare, the infant mortality rate for all causes in developed countries like the U.S. or Canada is about 0.5% (5 deaths per 1,000 births)—meaning GBS-related deaths are far less common.
Think of it like this: If you filled a theater with 1,000 babies who developed GBS infections, 20-30 babies might not make it, while 970-980 would recover with treatment.
This highlights that while GBS infection can be serious, it is thankfully treatable in most cases with modern medical care.
Monitoring Your Baby After Birth
If you are GBS-positive, GBS unknown, or had risk factors during labor, your healthcare team will monitor your baby for signs of infection if you had your baby in the hospital, birth center or at home with a midwife. You can also play an active role in observing your baby at home, particularly in cases of free birthing/wild pregnancies where you do not have a medical professional monitoring your baby.
What to Monitor:
Watch for signs like fever, lethargy, breathing problems, or poor feeding.
Take note of changes in your baby’s behavior: Are they unusually sleepy, fussy, or not waking to feed?
Medical Follow-Up:
If antibiotics were used during labor, let your pediatrician know so they can assess the baby’s health and microbiome support needs (e.g., probiotics).
If you had a GBS-positive test but declined antibiotics, ensure your care team is aware to closely monitor your newborn.
If your baby develops a GBS infection, they will need to be treated in the hospital. The main treatment is antibiotics, usually given through an IV (a tiny tube inserted into their vein).
Here’s how it works:
Antibiotics: The most common ones used are penicillin or ampicillin, which help fight off the bacteria causing the infection. Sometimes, another antibiotic like gentamicin may be added for extra coverage.
Supportive Care: If the baby is having trouble breathing, feeding, or maintaining their temperature, they may need extra care, such as oxygen, fluids through the IV, or feeding support until they’re stable.
Monitoring: Doctors and nurses will closely monitor your baby to ensure they’re responding to the treatment. Most babies start improving within a day or two, but antibiotics are typically given for 7-10 days, depending on the severity of the infection.
In severe cases, like meningitis or sepsis, treatment may take longer, but early treatment often leads to good outcomes. The healthcare team will keep you updated every step of the way.
The Controversy Around USe of antibiotics for prevention of Group B Strep infection
The topic of Group B Strep (GBS) can spark debate, particularly in high-resource countries where medical interventions are sometimes overused. For those who test positive—roughly one-third of pregnant women—preventive antibiotics during labor are routinely recommended. However, this approach can feel unnecessary to some, especially considering that 98-99% of babies born to GBS-positive mothers will not develop an infection.
It’s important to note that antibiotics are often given prophylactically (just in case) to birthing women, regardless of their GBS status, if their waters have been ruptured for an extended period—commonly referred to as prolonged rupture of membranes. This typically means that if your waters break 18-24 hours before your baby is delivered, you’ll likely be offered antibiotics as a precaution, unless you choose to decline.
Concerns often center around the overuse of antibiotics and the potential impact on a newborn’s developing microbiome. Antibiotics, while effective in reducing the risk of GBS infection, can disrupt the balance of beneficial bacteria, which play a critical role in a baby’s long-term gut health and immune system development.
The microbiome refers to the collection of bacteria that live in and on the body, playing a critical role in digestion, immunity, and overall health. During birth, babies are exposed to their mother’s bacteria, which helps establish their gut microbiome. When antibiotics are administered during labor, they can disrupt this process by reducing the diversity of beneficial bacteria passed to the baby.
Research suggests that antibiotics during labor may:
Decrease beneficial bacteria, like Bifidobacteria and Lactobacillus, in the newborn’s gut.
Potentially increase the risk of conditions such as allergies, asthma, and eczema later in life, though the evidence is still evolving.
How Antibiotics and Birth Practices Influence the Infant Microbiome
Your microbiome begins developing even before birth. In fact, some research shows that fetuses swallow small amounts of maternal gut bacteria present in the amniotic fluid (the “waters” surrounding the baby in the womb).
However, the most significant seeding of the microbiome happens during birth, when a newborn is first exposed to bacteria from the mother’s vagina and/or skin (Gensollen et al., 2016). This is one reason why babies born vaginally often experience better health outcomes during infancy and childhood as the microbiome seeded through a vaginal birth typically contains more beneficial bacteria compared to a c-section delivery (Milani et al., 2017).\
A Canadian study (Azad et al., 2016) followed babies to one year of age whose mothers received antibiotics during labor to examine the impact beyond the initial newborn period.
By three months of age, babies exposed to antibiotics at birth had lower levels of Bacteroidetes (a beneficial bacteria) and reduced overall microbiome diversity. These changes were observed regardless of whether the baby was exclusively breastfed or not. The effects were most pronounced in babies born via Cesarean section. Cesarean-born infants also exhibited higher levels of potentially harmful bacteria, such as Clostridium, Enterococcus, and Streptococcus.
By one year of age, most of these differences had resolved, suggesting that antibiotics primarily have a short-term impact on the infant microbiome. However, negative effects persisted in certain groups, particularly babies born via unplanned Cesarean who were not breastfed for at least three months. Some researchers caution that even temporary disruptions to the microbiome during the first year of life could have long-term implications for the development of the baby’s immune system (Zimmerman & Curtis, 2019).
These microbiome changes are consistent with the effects of IV antibiotics like penicillin or ampicillin, which target gram-positive bacteria such as Group B Strep but also disrupt beneficial bacteria like Bacteroidetes. This imbalance can result in an overgrowth of gram-negative bacteria, further altering the microbiome.
In summary, IV antibiotics given during childbirth can cause short-term dysbiosis (disruption) in the infant gut microbiota. However, these effects can often be mitigated by vaginal birth and breastfeeding, which help restore beneficial bacteria. The long-term implications for the microbiome and immune health as the child grows are not yet fully understood and require further research.
For mothers who have a Cesarean, receive antibiotics, or choose not to breastfeed, additional measures may support the baby’s microbiome recovery. Options such as donor human milk, probiotic supplementation, or probiotic-enriched formula can help reduce the potential disruptions caused by antibiotics and birth interventions.
Informed Decision-Making
The decision to take antibiotics during labor is ultimately the mother’s choice, although it is not always portrayed that way. It’s essential that women are fully informed of both the risks of GBS transmission and the potential effects of antibiotic use, so they can make the choice that feels right for them and their baby.
When given all the facts, mothers can weigh the benefits and risks of both options and make a fully informed decision. Remember, you are the ultimate authority in your birthing experience, and it’s your right to choose the path that aligns with your values and priorities.
Additional Resources for Further Information
Evidence Based Birth (EBB):
A highly trusted resource providing research summaries on GBS testing, risks, and treatment options.
Visit: www.evidencebasedbirth.com
Search for: "Group B Strep and Antibiotics in Labor"
Group B Strep Support (GBSS):
A UK-based charity offering comprehensive resources, FAQs, and research updates about GBS.
Visit: www.gbss.org.uk
Cochrane Library:
A leading source for systematic reviews on healthcare topics, including GBS screening and treatments.
Visit: www.cochranelibrary.com
Search for: “Group B Streptococcus”
La Leche League International (LLLI):
Offers information on breastfeeding, including how antibiotics during labor might impact the newborn's gut microbiome.
Visit: www.llli.org
World Health Organization (WHO):
Provides global guidelines and research on GBS prevention and management.
Visit: www.who.int
Search for: "Group B Streptococcus in pregnancy"
PubMed (National Library of Medicine):
A research database with peer-reviewed studies on GBS, antibiotics, and the microbiome.
Visit: pubmed.ncbi.nlm.nih.gov
Search for terms like “GBS antibiotics microbiome newborn” for the latest studies.
Microbirth (Book & Documentary):
A resource exploring the critical role of the microbiome in birth and how interventions like antibiotics may affect long-term health.
Learn more: www.microbirth.com
These sources offer balanced, research-backed information to help women make informed decisions about GBS, antibiotics, and their options during pregnancy and labor. I recommend checking multiple sources to feel confident in your choices.
