Group B Streptococcus, also known as GBS is a type of bacteria that naturally inhabits the large intestine and can move down to the rectum, vagina, and urinary tract. In this post we will cover “what is GBS in pregnancy?,” “GBS testing in pregnancy,” “how do you get GBS in pregnancy,” “what causes GBS in pregnancy,” and how to prevent GBS in pregnancy!
What is GBS in Pregnancy?
At any given time worldwide, as many as 30% of people are colonized with GBS. It can cause infection in people at any age; however, it generally does not seem to provide benefits or cause harm to people. Most people colonized with GBS will never develop an infection, and it is considered physiological or normal (ACOG, 2019).
Still, GBS can cause infections when someone’s immune system is not functioning at its highest, such as when you’re very young, if you have a chronic disease, or when you are very old (Steer et al., 2020).
Early and Late Onset GBS Disease:
There are two main types of infant GBS diseases.
Early-onset GBS Disease:
Occurs less than 7 days of life.
Early-onset GBS disease is defined as detecting GBS in the blood, cerebrospinal fluid, or lungs, along with the infant showing signs of a clinical condition such as sepsis, meningitis, or pneumonia during the first week of life (Seale et al. 2014).
Early onset GBS can be transmitted vertically from mom to baby through labor and birth and is responsible for potentially serious adverse events in the infant. Most commonly, these events are sepsis and pneumonia, and less commonly, meningitis.
Signs and Symptoms of a Newborn with Early-Onset GBS Disease include:
(Puopolo et al. 2019)
- Tachycardia
- Tachypnea
- Lethargy
- Appearing weak, low muscle tone
- Fever of 100.4 F or higher
- Poor feeding
- Irritability
- Grunting or nasal flaring
- Projectile vomiting
- The baby’s skin pulling in sharply around the ribs or at the base of the throat when breathing in
- Bulging soft spots on the head
- Brick dust color in the baby’s diaper more than 3 days after birth
- No wet diaper in 24 hours
If a baby has early-onset GBS disease, symptoms will appear shortly after birth (Puopolo et al. 2019). In a study of 148,000 infants born between 2000 and 2008, almost all the 94 infants who developed early-onset GBS disease were diagnosed within one hour of birth. Therefore, researchers believe that early-onset GBS disease usually begins before birth (Tudela et al. 2012).
Late-onset gbs disease:
Arises from 1 week-3 months of life. Either type of GBS disease can cause pneumonia, sepsis, meningitis, and death. However, meningitis is more common with late-onset GBS (7% with early-onset disease vs. 25-30% of late-onset disease) (Nanduri et al., 2019).
Late-onset GBS develops from contact with hospital personnel or other members of the community who carry the GBS bacteria on their skin and have contact with the baby.
What Causes GBS in Pregnancy?
As mentioned above, many people carry GBS and don’t have issues! GBS is a normal part of the microbiome for some people. To help reduce your risk of carrying GBS during your pregnancy, or at least minimize colonization, taking a probiotic blend, eating a good diet, and using breast milk can all help increase the numbers of good bacteria in your microbiome.
When a mother has GBS, it can be transmitted vertically from mom to baby through labor and birth and is responsible for potentially serious adverse events in the infant. This is early-onset GBS disease.
Before a baby is born, the microbiome has not been seeded, and there is a window of opportunity for harmful bacteria to potentially impact human health and disease (Gensollen et al. 2016). Still, there are ways that fetuses are protected from infection during pregnancy.
One major protective factor is the chorioamnion, also known as the fetal membranes, or the “bag” or “sac” surrounding the amniotic fluid. The membranes are an essential barrier preventing bacteria from entering the uterus and fetus (Parry & Strauss 1998).
However, once the fetal membranes rupture, there is a potential pathway for infection. If GBS is present, it can travel from the vagina up into the amniotic fluid and uterus in what is called ascending infection or vertical transmission. The fetus may even swallow some GBS while practicing breathing in-utero, potentially leading to early-onset GBS infection (Puopolo et al. 2019).
Late-onset GBS disease develops from contact with hospital personnel or other members of the community who carry the GBS bacteria on their skin and have contact with the baby.
Is GBS in Pregnancy Common?
The CDC shares that about 1 in 4 pregnant women carries GBS bacteria in their body (CDC, 2022). Further, they recommend that doctors and midwives test pregnant women for GBS bacteria when they are 36 through 37 weeks pregnant.
Is GBS Dangerous in Pregnancy?
GBS-positive or “at-risk” pregnant women are the focus in preventing early-onset GBS infection. For newborn babies born with immature immune systems, GBS can cause a serious infection that usually requires a stay in the NICU (Puopolo et al. 2019). Risks of GBS in pregnancy include urinary tract infections (UTIs), pre-term birth, and stillbirth. However, GBS is the cause of only 1-2% of UTIs in pregnancy and only 1-2% of stillbirths (Steer et al., 2020).
However, if a baby is born from a mother with GBS, this does not mean the baby will get GBS infection. But if the baby does, the baby is at risk for pneumonia, sepsis, meningitis, and death.
What is the Risk of Death with Infant GBS Disease?
When a baby is exposed to GBS in labor and birth, he or she has a 50% chance of becoming colonized with GBS. Most healthy, full-term infants will develop their own colonization of the skin and gut as a result, without developing an infection.
However, a small percentage who get exposed will become infected. The risk of a baby developing a serious, life-threatening GBS infection, according to the CDC, is 1-2%.
The mortality rate among babies with early-onset GBS is 2-3% for full-term infants. For premature babies, it is as high as 18-35% with an average of 21.6%.
In the U.S., which is considered a high-resource country (despite the high, and rising, number of perinatal care deserts), approximately 6.9% of full-term infants with early GBS disease will die from their infection. Death rates are higher (19.2%) in preterm infants in early-onset GBS disease (Nanduri et al., 2019).
Furthermore, newborns in high-resource countries who will most likely survive if they have early-onset GBS disease, usually require long, expensive stays in a NICU. In the NICU, infant receive invasive interventions to treat serious illness from pneumonia, sepsis, or meningitis, caused by GBS infection.
In middle- to high-resource countries, up to 18% of infants survive GBS meningitis (infection of the brain and spinal cord) end up with moderate to severe neurodevelopmental problems, including long-term cognitive, motor, vision, or hearing impairment (Kohli-Lynch et al., 2017).
Very little is known about the long-term health risks of infants who have GBS with sepsis or pneumonia, but some may have long-term developmental problems as well (Kohli-Lynch et al., 2017).
Why Test for Group B Strep in Pregnancy?
Countries generally choose the “universal screening approach” or the “other risk factor approach.”
The Universal Screening Approach: Includes screening all pregnant women for GBS at 35-37 weeks (in the U.S., this changed to 36-37 weeks) and treating everyone who tests positive with appropriate antibiotics during labor. This method is recommended by the World Health Organization and is currently used in 60 countries, including the U.S., Canada, Mexico, Brazil, Chile, France, Germany, and more (Le Doare et al. 2017).
The Other Risk Factor Approach: Is when the pregnant woman is not screened for GBS. Instead, pregnant women are treated with antibiotics in labor if they have one or more of these other risk factors:
- GBS in the urine at any point in pregnancy
- Previously gave birth to an infant at any point in pregnancy
- Pre-term labor
- Fever during labor
- Water has been broken for more than 18 hours
It is important to note that the specific risk factors chosen may vary slightly from country to country. The “other risk factor” method is currently used in 25 countries, including the United Kingdom, Ireland, the Netherlands, Norway, Sweden, Finland, Iceland, Saudi Arabia, Tanzania, South Africa, India, Bangladesh, Thailand, the Philippines, and New Zealand (Le Doare et al. 2017).
Can GBS in Pregnancy Go Away?
In one study conducted in the United States, researchers did a urine culture test twice for each pregnant woman, once at 35-36 weeks and once more during labor. They compared the 35–36-week results to results from the culture taken during labor. Of the pregnant women who screened negative for GBS at 35-36 weeks, 91% were still GBS-negative when the culture was done during labor. The other 9% became GBS positive, meaning these 9% were “missed” cases and were carriers of GBS.
Of all the women who screened positive for GBS at 35-36 weeks, 84% were still GBS-positive when the culture was taken during labor. However, 16% of the GBS-positive pregnant women became GBS-negative by the time they went into labor. Therefore, 16% of the GBS-positive women received unnecessary antibiotics (Young et al. 2011).
So, yes. Women may test positive or negative one week, then the test may change another week if tested again.
Will Antibiotics Harm My Baby’s Microbiome?
There are a number of studies demonstrating adverse effects to the microbiome from antibiotics during pregnant and birth. In one study of 52 newborns, half of their mothers received antibiotics in labor for GBS and the other half didn’t (this group was negative for GBS), there was a decreased number of the beneficial bacteria, Bifidobacterium, in the antibiotic group (Aloisio et al., 2014). Some studies suggest that the newborn microbiome changes resolve within two months.
Evidence suggests that the use of antibiotics for less than 24 hours during labor is not a source of long-term microbiome damage, nor risk of eczema later in life (Wohl et al., 2015).
Studies also suggest that any short-term damage can be mitigated by breastfeeding and possibly the use of probiotics given to the newborn!
However, if you receive greater than 24 hours of antibiotic treatment in labor, this was associated with an increase in eczema at 2 years of age (Wohl et al., 2015).
Another study compared babies at 3 months who had been exposed to antibiotics versus babies who had not, breastfeeding was an important factor. The babies who had been exposed to antibiotics and who were exclusively breastfed for at least 3 months had more similar microbiomes to those babies who were never exposed to antibiotics but were not exclusively breastfed (Azad et al., 2016).
Some babies did have persistent changes even at 1 year after birth, after which the microbiomes of babies tend to become similar regardless of type of birth or whether antibiotics were used.
Bottom line on infant antibiotic exposure:
Overall, it appears that if antibiotics are used for less than 24 hours, the risk is short term. Additionally, breastfeeding for at least 6 months may mitigate the effects of antibiotics used in labor for less than 24 hours. Unfortunately, antibiotics don’t only affect the bad bacteria, they also impact other bacteria including probiotics (the good bacteria). Therefore, adding in the infant probiotic drops in addition to breastfeeding can really help improve the infant microbiome as well.
Still, this research does not take into account the impact of microbiome alterations in the first year of life on the development of the immune, digestive or nervous systems, therefore much more research is needed to compare the long-term health effects of early antibiotic use on the microbiome.
What is the GBS Vaccine?
While maternal GBS colonization was historically the strongest risk factor for disease development, one study documented that up to 80% of early-onset GBS cases in term neonates occur in neonates born to mothers with negative antenatal GBS screening (Stoll et al. 2011).
Why some people see a need for a GBS vaccine:
- Intrapartum (in-labor) antibiotics do not prevent GBS 100% of the time
- In-labor antibiotics have side effects and can negatively impact the microbiome
- In- labor antibiotics do not prevent other GBS effects such as pre-term labor. stillbirth, or late onset GBS infection in newborns
- Pregnant women in low-resource parts of the world have difficulty accessing GBS testing and antibiotic treatment during labor
In an analysis published in 2017, Seale et al. predicted that, with a GBS vaccine that works 80% of the time and is administered to more than half of pregnant women in the world, we could prevent 23,000 stillbirths, 127,000 cases of early GBS disease in infants, and 37,000 infant deaths each year. The researchers also calculated that vaccinating half of all pregnant people worldwide would be more effective at preventing disease and death than carrying out GBS screening and providing in-labor antibiotics to more than 50% of pregnant people.
Currently, public health experts are optimistic about the possible positive impact that GBS vaccines could have around the world: “An effective maternal GBS vaccine offers an all-encompassing approach to reducing GBS disease, and, as vaccine strategies can achieve high coverage in even the most challenging settings, it is likely to be a more equitable intervention than intrapartum antibiotic prophylaxis. Maternal GBS vaccination can potentially reduce this disease burden worldwide, within the next generation and including the poorest families” (Seale et al. 2017).
How to Prevent GBS in Pregnancy
If you aren’t interested in the GBS vaccine or just don’t have access to it since none of them are completely done with the phases of testing, there are other ways you can prevent or minimize GBS colonization!
preventing gbs with Breast milk
Another potentially effective method of suppressing GBS colonization in mothers is using breast milk. In 2017, three different research teams found that human milk oligosaccharides (HMOs) inhibit the growth of GBS in petri dishes (Lyon and Doran, 2022). Then in 2022, researchers found that topical application of HMOs can inhibit GBS in the vaginas of laboratory mice without impacting the rest of the vaginal microbiome (Mejia et al. 2022).
Human research has not yet been conducted on this potential use of HMOs for GBS colonization. However, this research might suggest that newborns born from GBS-positive mothers may have a reduced risk of GBS infection if they are breastfed, as the HMOs may benefit from reducing GBS colonization in their bodies (Ackerman et al. 2017).
preventing gbs with probiotics
There are different types of bacteria that make up your microbiome. The bacteria can have good, neutral, or negative impacts on your body. The microbes that have good effects on your body are called probiotics. Probiotics positively influence many aspects of your body, including energy, digestion, bran activity (behavior and emotions), drug metabolism, the release of essential vitamins, protection against infections, and more (Trinh et al., 2018).
Taking probiotics in pregnancy should help lower your risk of testing positive for GBS in the third trimester. Probiotics, such as Lactobacillus, make the vagina more acidic, which inhibits growth of GBS (Hanson et al., 2022).
However, a randomized trial with 83 participants showed that the probiotic group had fewer GI symptoms at 36 weeks compared to the placebo group. But there was no difference in rates of testing positive for GBS at 36 weeks. Further, the participant’s pill bottle caps showed that both groups only took their assigned pills only about 51-60% of the time (Hanson et al. 2023).
There were no adverse health outcomes in either group. Considering the details of this study, it seems there is more research to be done to look at how probiotic use in pregnancy may impact GBS testing results.
Colloidal silver for gbs in pregnancy:
Although silver does have antibacterial properties, there is no research on using colloidal silver in pregnancy nor for GBS colonization.
Further, other researchers have reported serious toxicity and health risks (Leino et al., 2021).
When to Treat GBS in Pregnancy?
You can begin using natural methods of preventing GBS colonization at any time in your pregnancy! Or, if you’re interested in a GBS vaccine, speak with your OB-GYN or midwife to see if they have access to it for you.
Further, if you test positive for GBS colonization or have the risk factors we discussed, you can use the data from this post to help you decide if receiving intrapartum antibiotic prophylaxis (IAP) is something you want.
Lastly, some people decide to avoid (IAP) and if their infant starts showing symptoms of early- or late-onset GBS infection, then they take them to the hospital. However, this may lead to more long and expensive NICU admissions in total for infants whose mothers used this approach.
Summary:
GBS is a naturally occurring bacteria that generally can only harm immune-compromised people and infants. About 1 in 4 pregnant women carry GBS bacteria.
Early-onset GBS infection makes up most of the infant deaths from GBS disease and is passed to the infant from the mother through labor and birth.
Late-onset GBS disease arises from 1 week-3months of life and more commonly than early onset, leads to neonatal meningitis.
When a baby is exposed to GBS in labor and birth, he or she has a 50% chance of becoming colonized with GBS and a 1-2% chance of developing a serious, life-threatening GBS infection.
Further, the mortality rate among babies with early-onset GBS is 2-3% for full-term infants. For premature babies, it is as high as 18-35% with an average of 21.6%.
GBS testing can show a positive result one week and a negative result another week, or vice versa depending on the number of GBS bacteria present at each test.
If in-labor antibiotics are used for less than 24 hours, long-term microbiome effects can be mitigated with breastfeeding for at least 6 months and, for extra support, using infant probiotic drops.
If in-labor antibiotics are used for more than 24 hours, this was associated with an increase in eczema at 2 years of age, therefore, may have some long-term microbiome effects.
Some ways to effectively reduce GBS colonization in pregnancy and for your baby after birth include breast milk and probiotics.
Questions or Comments?
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Talk soon, mama!
– Katelyn Lauren
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