What is Group B Strep?
Group B Streptococcus (GBS) is a type of bacteria that can cause illness in people of all ages. In newborns, GBS is a major cause of meningitis (infection of the lining of the brain and spinal cord), pneumonia (infection of the lungs), and sepsis (infection of the blood) (CDC 1996; CDC 2005; CDC 2009).
Group B strep lives in the intestines and migrates down to the rectum, vagina, and urinary tract. All around the world, anywhere from 10-30% of pregnant women are “colonized” with or carry GBS in their bodies (Johri et al. 2006). Using a swab of the rectum and vagina, women can test positive for GBS temporarily, on-and-off, or persistently (CDC 2010).
Being colonized with GBS does not mean that a woman will develop a GBS infection. Most women with GBS do not have any GBS infections or symptoms. However, GBS can cause urinary tract infections, pre-term birth, and GBS infections in the newborn (Valkenburg-van den Berg et al. 2009; CDC 2010).
In this article, I will focus on Group B Strep in pregnancy in the United States, along with some information about other countries.
Are some women more likely to carry GBS?
Researchers have looked at the risk factors for GBS in young, non-pregnant women (Feigin, Cherry et al. 2009). Women with these factors may be more likely to carry GBS:
- Multiple sexual partners
- Male-to-female oral sex
- Frequent or recent sex
- Tampon use
- Infrequent handwashing
- Less than 20 years old
How often do newborns become infected with GBS?
There are 2 main types of GBS infection in newborns: early infection and late infection. In this article we will focus on early infection, which occurs in the first 7 days after birth. When a baby has an early GBS infection, symptoms usually appear within the first 12 hours, and almost all babies will have symptoms within 24-48 hours (CDC 2010). In a study of 148,000 infants born between 2000 and 2008, almost all of the 94 infants who developed early GBS infection were diagnosed within an hour after birth—suggesting that early GBS infection probably begins before birth (Tudela et al. 2012).
Early infection is caused by direct transfer of GBS from the mother to the baby, usually after the water breaks. The bacteria travel up from the vagina into the amniotic fluid, and the fetus may accidentally swallow some of the bacteria into the lungs—leading to an early GBS infection. Babies can also get GBS on their body (skin and mucous membranes) as they travel down the birth canal. However, most of these “colonized” infants stay healthy (CDC 2010).
In 1993-1994, the American Congress of Obstetricians and Gynecologists and the American Academy of Pediatrics recommended screening all pregnant women for GBS and treating GBS-positive women with intravenous (IV) antibiotics during labor. Since that time, we have seen a remarkable drop in early GBS infection rates in the U.S.—from 1.7 cases per 1,000 births in the early 1990’s, to 0.25 cases per 1,000 births today (CDC 2012).
If a mother who carries GBS is not treated with antibiotics during labor, the baby’s risk of becoming colonized with GBS is approximately 50% and the risk of developing a serious, life-threatening GBS infection is 1 to 2% (Boyer & Gotoff 1985; CDC 2010; Feigin, Cherry et al. 2009). As I noted earlier, being colonized is not the same thing as having an early GBS infection– most colonized babies stay healthy.
On the other hand, if a woman with GBS is treated with antibiotics during labor, the risk of her infant developing an early GBS infection drops by 80%. So for example, her risk could drop from 1% down to to 0.2%. (Ohlsson 2013)
What is the risk of death if the baby has an early GBS infection?
Researchers have estimated that the death rate from early GBS infection is 2 to 3% for full-term infants. This means of 100 babies who have an actual early GBS infection, 2-3 will die. Death rates from GBS are much higher (20-30%) in infants who are born at less than 33 weeks gestation (CDC 2010).
Although the death rate of GBS is relatively low, infants with early GBS infections can have long, expensive stays in the intensive care unit. Researchers have also found that up to 44% of infants who survive GBS with meningitis end up with long-term health problems, including developmental disabilities, paralysis, seizure disorder, hearing loss, vision loss, and small brains. Very little is known about the long-term health risks of infants who have GBS without meningitis, but some may have long-term developmental problems (Feigin, Cherry et al. 2009; Libster et al. 2012).
Are some newborns more likely to get early GBS disease?
The primary risk factor for early GBS infection is when the mother carries GBS. However, there are some things that increase the risk of early GBS infection:
- Being African American (CDC 2012)
- *Being born at less than 37 weeks (Boyer &Gotoff 1985; Velaphi et al. 2003; Heath et al. 2009)
- *A long period between water breaking and giving birth (Boyer &Gotoff 1985; Velaphi et al. 2003; Heath et al. 2009)
- Water broke before going into labor (premature rupture of membranes) (Adair et al. 2003)
- *High temperature during labor (> 99.5 F or 37.5 C) (Boyer & Gotoff 1985; Adair et al. 2003; Velaphi et al. 2003; Heath et al. 2009)
- Infection of the uterus (aka “chorioamnionitis”) (Adair et al. 2003)
- Mother previously gave birth to an infant who had an early GBS infection (CDC 2010)
- Intrauterine monitoring during labor (Adair et al. 2003)
*These are the major risk factors. About 60% infants who develop early GBS infection have no major risk factors, except for the fact that their mothers carry GBS (Schrag et al. 2002).
How accurate is testing for GBS?
The CDC recommends measuring GBS with a culture test at 35-37 weeks of pregnancy. This is done by swabbing the rectum and vagina with a Q-tip, and then waiting to see if GBS grows. It takes about 48 hours to get the results back. The goal is to get the results back before labor begins (CDC, 2010).
A culture test during labor is considered the “gold standard,” but this method is not used in practice because it takes too long to get results back. In a recent, high-quality study, researchers did the culture test twice– once at 35-36 weeks and once during labor. They compared the 35-36 week test to the gold standard.
Of the women who screened negative for GBS at 35-36 weeks, 91% were still GBS-negative when the gold standard test was done during labor. The other 9% became GBS positive. These 9% were “missed” GBS cases, meaning that these women had GBS, but most (41 out of 42) did not receive antibiotics.
Of the women who screened positive for GBS at 35-36 weeks, 84% were still GBS positive when the gold standard test was done during labor. However, 16% of the GBS-positive women became GBS-negative by the time they went into labor. These 16% received unnecessary antibiotics (Young et al. 2011).
Is there a faster test that could be used in labor?
It’s possible that a rapid-test for GBS during labor may be a better option for some women. In the same study mentioned above, researchers compared the 35-36 week culture test and the in-labor rapid test to the gold-standard test (culture during labor).
The researchers found that the 35-36 week culture test only identified 69% of the women who actually had GBS during labor. Meanwhile, the in-labor rapid test was much more sensitive—it identified 91% of women with GBS during labor (Young et al, 2011).
In a 2012 study in France, researchers followed a hospital as it switched from prenatal testing to in-labor testing for GBS. With the in-labor rapid GBS test, more mothers with GBS were identified (17% vs. 12%), there were fewer cases of early GBS infection in newborns (0.5% vs. 0.9%), and the financial cost was the same (El Helali et al. 2012).
One drawback of rapid-testing is that it can still take up to 60 minutes to get the results back, and women would have to wait to get antibiotics until the results came in (Honest et al. 2006; Young et al. 2011). The CDC says that the ideal rapid test for GBS could be done at the bedside in less than 30 minutes (CDC, 2010).
Right now there is one rapid GBS test on the market that claims it can be done within 30 minutes. However, a researcher who used this test in a clinical study says that this same test actually takes 50 minutes to carry out—5 minutes to prepare the sample, and 45 minutes to run the results (Personal communication, M. Hacker, April 2013). The price of this test is not listed online– so we don’t know if it’s affordable. Finally, researchers have not done studies yet to find out whether the rapid test is cost-effective.
What is the evidence for antibiotics during labor to prevent early GBS infection?
To answer this question, I will walk you through the most important studies that led to how we most commonly try to prevent early GBS infections in the U.S. today.
GBS emerged as a widespread threat to newborns in the early 1970’s. At that time, 1.7 of every 1,000 infants had early GBS infection (CDC 2010). In 1973, a researcher proposed giving pregnant women penicillin to stop early GBS infections in infants (Franciosi et al. 1973).
First, researchers tried giving penicillin to women before labor, but this didn’t work. Although penicillin temporarily lowered GBS levels, by the time women went into labor the GBS levels were back up again (Gardner et al. 1979).
Next, researchers tried giving antibiotics to women with GBS during labor. In the late 1980’s, three groups of researchers in the U.S., Spain, and Finland randomly assigned women with GBS to either receive IV antibiotics during labor (penicillin or ampicillin) or no antibiotics (Boyer & Gotoff 1985; Tuppurainen and Hallman 1989; Matorras et al. 1991).
In a recent Cochrane review, researchers combined the results of these 3 studies that had a total of 500 pregnant women. They found that when women with GBS had antibiotics during labor, their infants risk of catching early GBS infection dropped by 83% (Ohlsson & Shah 2013).
As the Cochrane reviewers noted, there were quite a few limitations to these 3 studies. In their summary, the reviewers said “There is no valid information from these three small, old, and biased trials to inform clinical practice.” However, this statement is biased. A more appropriate conclusion would be that there is some valid information from these studies, along with some limitations to the evidence.
Based on information from these 3 studies, in 1996, the CDC recommended 2 ways to prevent early GBS infections:
- The “universal approach.” Screen all pregnant women at 35-37 weeks and treat everyone who is positive with antibiotics during labor (this is the method that is currently used in the U.S.)
- The“risk-based approach.” Treat laboring women with antibiotics if they have one or more of these risk factors: GBS in the urine at any point in pregnancy, previously gave birth to an infant with early GBS infection, goes into labor at less than 37 weeks, has a fever during labor, or water has been broken for more than 18 hours (this is the method that is currently used in the United Kingdom)
In 2002, the CDC revised their guidelines to recommend the universal approach. This decision was based on an important study published in the New England Journal of Medicine (Schrag et al. 2002). In this study, researchers used CDC lab results and chart reviews to look at 629,912 live births that took place in the U.S. between the years 1998-1999.The researchers randomly selected 5,144 of these births to study, plus all 314 infants who were born with early GBS. They used hospital records to label women as receiving the universal approach (52%) or the risk-based approach (48%).
The results? There were 0.5 infants born with GBS per every 1,000 women. Women in both groups received antibiotics about a third of the time. But women whose care providers used the universal approach had a 54% reduction in the risk of early GBS infection compared to women whose care providers used the risk-based approach. This means that the universal approach worked better than the risk-based approach.
In 2002-2003, the same group of researchers looked at 819,528 births in the U.S. to see whether the revised guidelines had been put into practice. Like the previous study, the researchers picked a random sample of women and infants to analyze, along with the 254 infants who had early GBS infection. Between 1999 and 2002, use of the universal approach rose from about 50% to 85%, and use of antibiotics during labor rose from 27% to 32%.
This time around, there were 0.32 infants born with early GBS per every 1,000 women (down from 0.5 cases per 1,000 only four years earlier). When researchers looked at the infants born at 37 weeks or later who had early GBS, only 18.0% were born to women who were not screened. Most of the cases of GBS in term infants (61%) happened in women who had been screened but tested negative for GBS. The researchers concluded that universal screening and antibiotic use cannot be expected to prevent 100% of early GBS infections, and that if we want to further lower GBS infection rates, then we will need access to rapid testing and vaccines against GBS (Van Dyke et al. 2009).
What is the best time to receive antibiotics for GBS?
The CDC recommends that antibiotics be given every 4 hours, starting more than 4 hours before birth. Recent evidence supports these recommendations. In 2013, researchers looked at 7,691 live births that took place during 2003-2004 in the U.S. (randomly selected out of >600,000 births), along with 254 infants who had early GBS infection (Fairlie et al., 2013). About 1 in 3 women had antibiotics during labor (31%), and 59% of women received antibiotics more than 4 hours before birth.
When penicillin or ampicillin was given more than 4 hours before birth, it was effective 89% of the time. In contrast, giving antibiotics 2-4 hours before birth was effective 38% of the time. Antibiotics given less than 2 hours before birth were effective 47% of the time. When Clindamycin (another antibiotic) was used in place of penicillin, it worked very poorly (only 22% effective). There was no statistical difference between the 2-4 hour window and the 2-0 hour window, so even though the percentages look different, they are not statistically significant.
What are the potential benefits and harms of the universal screening and treatment approach?
- In clinical trials, using antibiotics (penicillin or ampicillin) decreases the risk of early GBS infection by 83%, although there are limitations to the quality of this evidence (Ohlsson 2013)
- Penicillin rapidly crosses the placenta into the fetal circulation (at non-toxic levels) and can prevent GBS from growing in the fetus or newborn (CDC 2010; Barber et al. 2008).
- In large studies in the U.S., the universal approach (screening and treating all GBS-positive women with antibiotics during labor) is associated with lower rates of GBS infections than giving antibiotics based on risk factors alone (Schrag et al. 2002).
- Antibiotic resistance has not been a problem with penicillin, the drug most commonly used to prevent early GBS infection (CDC 2010).
- Although rare, severe allergic reactions in mothers have been reported. The risk is estimated to be 1 in 10,000 for a severe reaction, and 1 in 100,000 for a fatal reaction. (Weiss and Adkinson 1988).
- There is an increase in the risk of maternal and newborn yeast infections. In one study, 15% of women who received antibiotics in labor had mother-baby yeast infections, compared to 7% of mothers who did not have antibiotics. (Dinsmoor et al. 2005).
- Other potential harms have to do with side effects related to the antibiotic that is used (click on the link to see a comprehensive list of potential side effects for each antibiotic, but keep in mind that most of the serious risks are rare): Penicillin, ampicillin, cefazolin, clindaymycin, and vancomycin.
- The potential medicalization of labor and birth (RCOG 2003).
What are the best antibiotics for someone who is allergic to penicillin?
Many women who have an allergy to penicllin can take Cefazolin instead. One advantage to Cefazolin is that (like penicillin) it crosses the placenta and reaches the fetus’s bloodstream. If a woman is at high risk for anaphylaxis with penicillin (click here to find out more), then the CDC recommends several different antibiotics instead of Cefazolin. Which antibiotic a woman can take depends on the results of her GBS lab tests. Alternative antibiotics include clindaymycin and vancomycin.
Unfortunately, clindamycin and vancomycin have never been tested in clinical trials for the prevention of early GBS infection. Clindamycin faces high rates of drug resistance, barely reaches the fetal bloodstream, and should never be used unless a woman’s GBS has been specifically tested and it is known that these antibiotics will work on her particular strain of GBS. Vancomycin can be used in someone who is highly allergic to penicillin and whose GBS is resistant to clindamycin. However, Vancomycin barely crosses the placenta to get into the fetal circulation. Finally, although some care providers may use erythromycin to prevent early GBS, the CDC states that erythromycin should never be used to prevent early GBS infection (CDC, 2010; Pacifici 2006).
If I have antibiotics, does this mean I will be continuously hooked up to an IV?
No. If you use the antibiotics, you will have an IV placed, but it only takes 15-30 minutes for the antibiotics to run in. The antibiotics are only given every 4 hours until birth, which for many women is only once or twice. When the IV is running, it should not limit positioning, walking, or even laboring in water. For the hours in between, the IV can be “hep-locked” or “saline-locked” and detached, so that you are free from the IV pole. For more information about saline locks, please read my article about saline locks during labor here.
Are there any other options?
One alternative to the universal approach is the “risk-based approach.” This is when you receive antibiotics based on other risk factors such as having a fever or your water being broken for more than 18 hours. This alternative is no longer recommended by the CDC. The number of women who receive antibiotics is roughly the same whether you choose the universal approach or the risk-based approach—about 30%. However, as already mentioned, evidence from large multi-state studies shows that in the U.S., the universal approach is more effective than giving antibiotics based on risk factors alone.
Chlorhexadine (aka Hibiclens) is a topical disinfectant that kills bacteria on contact. It binds easily to the skin and mucous membranes. In the vagina, the anti-GBS effects of chlorhexadine last from 3-6 hours. Chlorhexadine has been shown to be safe, is easy to administer, and only costs a few cents per use (Goldenberg et al. 2006).
However, although chlorhexadine reduces the risk of a newborn being colonized with GBS, it has not been shown to decrease the risk of actual GBS infections in newborns. As I said earlier in the article, there is a difference between being colonized and being infected. Colonized babies almost always stay healthy, while infected babies are very sick, and it is thought that an actual early GBS infection occurs when the fetus swallows infected amniotic fluid into the lungs. In a Cochrane review (Stade et al. 2004), researchers combined results from 5 randomized, controlled trials that compared vaginal chlorhexadine to a placebo on outcomes of 2,190 infants born to women who were GBS positive. There was a wide range in the quality of the studies, with only one study being very high quality.
Even though women who used vaginal chlorhexadine reduced their infants’ risk of being colonized with GBS by 28%, there was no difference in rates of early GBS infection between women who used the chlorhexadine and those who did not. There were no cases of infant deaths from GBS in either group. The only adverse effects that were reported were stinging and irritation. The researchers called for a large clinical trial to test chlorhexadine for the prevention of early GBS.
Chlorhexadine may potentially be beneficial for women living in poor countries where access to antibiotics is limited. In their review of the literature, Goldenberg et al. (2006) found 2 studies from developing countries (Egypt and Malawi) where researchers tested chlorhexadine in the vagina every 4 hours during labor and neonatal wipes shortly after birth. This is a lower level of evidence than the studies listed above, because neither of these were randomized, controlled trials. Instead, the researchers followed hospitals over a period of months when: 1) they did not use chlorhexadine, 2) they used chlorhexadine, and 3) they stopped using chlorhexadine. In both studies, researchers found that when chlorhexadine was used, there were immediate drops in newborn hospital admissions, newborn sepsis admissions, and newborn deaths due to infections. Unfortunately, researchers did not specifically count the number of GBS infections, just the overall number of babies who had admissions for sepsis.
So is chlorhexadine effective? The bottom line is that we don’t know with any certainty if it helps or not. Randomized, controlled trials show that in developed countries, chlorhexadine wipes during labor do not make any difference in early GBS infection rates. However, evidence from developing countries shows that chlorhexadine vaginal wipes PLUS newborn wipes may reduce sepsis rates in general. Chlorhexidine is likely better than nothing, but it cannot prevent the ascent of GBS in the amniotic fluid unless it is given before a woman’s water breaks and repeated before its effect wears off. Unlike IV antibiotics, there is no evidence that chlorhexadine can stop GBS from growing in the fetus before birth.
Garlic has antibacterial properties, and some websites recommend putting garlic in the vagina to eliminate GBS before the GBS test. However, there is very little evidence to back up this treatment. One group of researchers put garlic extract and GBS in a petri dish together (Cutler et al., 2009). They found that the garlic was able to kill the GBS within about 3 hours. However, this treatment has never been tested in people. Also, it’s important to understand that back in the 1970’s when researchers tried using penicillin during pregnancy, they found that the antibacterials temporarily lower levels of GBS, but levels almost always go up again by the time women go into labor. So by temporarily using garlic, this could help you get a negative test result, but the effect will wear off very quickly.
Some women choose to keep garlic or chlorhexidine in the vagina for the last 4 weeks of pregnancy or use either of these treatments regularly before their water breaks and before they go into labor. It’s possible that this may help decrease GBS levels before labor. However, we do not have any research evidence yet to support this practice. This means we have little evidence about the potential benefits and harms. For example, it is possible that long-term garlic or chlorhexidine use could potentially or theoretically have unexpected effects like premature rupture of membranes or increase other bacteria– even GBS– due to destruction of good bacteria, like lactobacilli. Until researchers examine the potential benefits and harms, there are a lot of unknowns related to this treatment.
Vaccines for GBS are under development, but are not available yet at this time (World Health Organization, 2005). There is a big push for a GBS vaccine for several reasons: 1) in-labor antibiotics do not prevent GBS infection 100% of the time (Velaphi et al., 2003), 2) in-labor antibiotics can have side effects, and 3) in-labor antibiotics do not prevent other GBS problems, such as preterm labor.
Taking probiotics (lactobacilli) is another remedy that people sometimes use to eliminate GBS in the vagina. In several studies, researchers have put vaginal lactobacilli (including a commercially available version) in a petri dish with different strains of GBS. They found that the lactobacilli strongly inhibited the growth of GBS by increasing the acidity of the environment. (Acikgov, 2005– article in Turkish; Zarate, 2006).
In a small clinical trial, researchers randomly assigned healthy, fertile (but non-pregnant) women to wear panty liners that were saturated with probiotics, or to wear placebo panty liners. The results showed that it is possible to transfer probiotics to the vagina using panty liners. The researchers also found that women who had higher levels of lactobacilli in the vagina had lower levels of GBS. However, although these results are promising, large clinical trials need to be conducted in pregnant women to determine if this is an effective way to prevent early GBS infection in newborns (Rönnqvist PD, 2007).
A few websites mention colloidal silver as a remedy for preventing GBS infection. Although silver has anti-bacterial properties, no known research studies have ever been conducted on taking colloidal silver to prevent a GBS infection—and no studies have ever looked at the safety of colloidal silver in pregnancy. The potential benefits and harms of this substance are unknown. In 1997, the FDA stated that colloidal silver is not safe or effective for any condition.
Can infants acquire a GBS infection from staff handling the newborn?
Researchers are quite certain that infants catch early GBS infections before they are born—most likely from GBS in the amniotic fluid. As mentioned earlier, almost all infants with early GBS infection show symptoms within an hour after birth. However, infants can catch “later” GBS infections from the hospital (nursery, hands of hospital staff and family members) or the community. This is one reason hand-washing is so important (Kliegman et al. 2011).
If I am GBS positive, and I don’t get the IV antibiotics for some reason, what kind of tests will my baby need to have?
As long as your baby appears to be doing well and you did not have any additional risk factors (<37 weeks, infection of the uterus, water broken >18 hours), then there is no need for your baby to have any special testing. There are some situations where the CDC recommends that a well-appearing infant have some blood tests. The CDC also recommends 48 hours of “observation”for infants who are born to GBS positive mothers, but there is no need to separate mom and baby for this observation period. To see a flow-chart with more details about newborn testing and observation, click here.
What do national organizations have to say?
In the United States:
The U.S. Centers for Disease Control and Prevention recommends universal screening for GBS at 35-37 weeks and in-labor antibiotics for all women who test positive.
- American Congress of Obstetricians and Gynecologists
- American Academy of Pediatrics
- American College of Nurse-Midwives
- American Academy of Family Physicians
- American Society for Microbiology
In the United Kingdom:
- The United Kingdom National Screening Committee states that pregnant women in the UK should not be screened for GBS. The UK follows the risk-based approach. This includes giving antibiotics in-labor to all women who have fever, prolonged rupture of membranes >18 hours, GBS in urine at any time during pregnancy, preterm labor, or a prior infant with GBS. This means that many women who are actually GBS negative receive antibiotics directed at GBS, just based on their risk factors. In the UK, the rate of early GBS infections is 0.5 per 1,000 births, which is slightly higher than the rate of 0.2 per 1,000 births in the U.S. In the UK, it is not considered cost effective to screen the whole population of pregnant women to lower the early GBS infection rate by 0.2-0.3 cases per 1,000.
- The Royal College of Obstetricians does not recommend routine screening for GBS during pregnancy. However, they do state that in-labor antibiotics could be considered if GBS was detected in passing or if women have any of the risk factors listed above. Many women are already receiving antibiotics for these reasons.
- There is controversy in the UK over the lack of access to GBS testing within the National Health Service. Group B Strep Support is a consumer-based charity that advocates for women to have access to GBS screening in the UK.
- The Society of Obstetricians and Gynaecologists of Canada (SOGC) recommends offering GBS screening to all pregnant women and treating those who are positive with IV antibiotics.
What is the bottom line?
- Since two-thirds of remaining early GBS infections are now due to false negative GBS test results, in the future we may benefit from a rapid in-labor test for GBS
- While probiotics, chlorhexadine, and garlic have the potential to reduce vaginal and newborn colonization with GBS, we do not have evidence yet to show that these strategies can prevent early GBS infections, since GBS infection usually occurs when GBS gains access to the amniotic fluid and gets into the fetus’ lungs during labor.
I would like to acknowledge my reviewers for helping maintain the quality of articles published at Evidence Based Birth. In particular, I would like to acknowledge Dr. Jessica Illuzzi, Associate Professor of Obstetrics, Gynecology, and Reproductive Sciences at Yale School of Medicine, for her expert review and assistance in writing this article. I would also like to acknowledge my 2 regular physician reviewers, and 2 other anonymous peer reviewers (a GBS researcher and a microbiologist).
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