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Group B Strep in Pregnancy

Evidence for Antibiotics and Alternatives



© By Rebecca Dekker, PhD, RN, APRN.


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. Using a swab of the rectum and vagina, women can test positive for GBS temporarily, on-and-off, or persistently.

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.


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. 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.


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.


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%. 

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%.


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.

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.


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  

*A long period between water breaking and giving birth

* Water broke before going into labor 

*High temperature during labor (> 99.5 F or 37.5 C)  

* Infection of the uterus (aka “chorioamnionitis”)

* Mother previously gave birth to an infant who had an early GBS infection 

* Intrauterine monitoring during labor 

*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 


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. 

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.


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.

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. The CDC says that the ideal rapid test for GBS could be done at the bedside in less than 30 minutes.


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. In 1973, a researcher proposed giving pregnant women penicillin to stop early GBS infections in infants.

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.

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.

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%.

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:

1. 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.)

2. 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 . 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.


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. 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. 


What are the potential benefits and harms of the universal screening and treatment approach?


Potential Benefits:  

* 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 

* Penicillin rapidly crosses the placenta into the fetal circulation (at non-toxic levels) and can prevent GBS from growing in the fetus or newborn.

* 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.

* Antibiotic resistance has not been a problem with penicillin, the drug most commonly used to prevent early GBS infection.


Potential harms:

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.


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.   

Other potential harms have to do with side effects related to the antibiotic that is used .

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.


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.

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. 


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.


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. 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.

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.


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. The CDC 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. 


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.


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.



1. Adair, C. E., L. Kowalsky, et al. (2003). “Risk factors for early-onset group B streptococcal disease in neonates: a population-based case-control study.” CMAJ 169(3): 198-203. Click here.

2. Ackigov, Z. C., S. Gamberzade et al. (2005). “Inhibitor effect of vaginal lactobacilli on group B streptococci.” Mikrobiyol Bul 39(1): 17-23. (Article in Turkish and unable to translate). Click here.

3. Barber, E. L., G. Zhao, et al. (2008). “Duration of intrapartum prophylaxis and concentration of penicillin G in fetal serum at delivery.” Obstetrics and gynecology 112(2 Pt 1): 265-270. Click here.

4. Boyer, K. M. and S. P. Gotoff (1985). “Strategies for chemoprophylaxis of GBS early-onset infections.” Antibiot Chemother 35: 267-280. Click here.

5. Centers for Disease Control and Prevention (CDC) (2009). “Trends in perinatal group B streptococcal disease- United States, 2000-2006.” MMWR Morb Mortal Wkly Rep 58: 109-112.

6. CDC (2010). “Prevention of perinatal group b streptococcal disease.” MMWR 59: 1-32. Click here.

7. CDC (2012). “ABCs report: Group B streptococcus, 2010.”   Retrieved March 10, 2013. Click here.

8. CDC (1996). “Prevention of perinatal group B streptococcal disease: a public health perspective. .” MMWR Recomm Rep 45: 1-24.

9. CDC (2005). “Early-onset and late-onset neonatal group B streptococcal disease– United States, 1996-2004.” MMWR Morb Mortal Wkly Rep 54: 1205-1208.

10. Cutler, R. R., Odent M, et al. (2009). In vitro activity of an aqueous allicin extract and a novel allicin topical gel formulation against Lancefield group B streptococci. J Antimicrob Chemother 63(1): 151-154. Click here.

11. Dinsmoor, M. J., R. Viloria, et al. (2005). “Use of intrapartum antibiotics and the incidence of postnatal maternal and neonatal yeast infections.” Obstetrics and gynecology 106(1): 19-22. Click here.

12. El Helali, N., Y. Giovangrandi, et al. (2012). “Cost and effectiveness of intrapartum group B streptococcus polymerase chain reaction screening for term deliveries.” Obstetrics and gynecology 119(4): 822-829. Click here.

13. Fairlie, T., E. R. Zell, et al. (2013). “Effectiveness of intrapartum antibiotic prophylaxis for prevention of early-onset group b streptococcal disease.” Obstetrics and gynecology 121(3): 570-577. Click here.

14. Feigin, R. D., J. D. Cherry, et al. (2009). Textbook of Pediatric Infectious Diseases, Saunders.

15. Franciosi, R. A., J. D. Knostman, et al. (1973). “Group B streptococcal neonatal and infant infections.” J Pediatr 82(4): 707-718. Click here.

16. Gardner, S. E., M. D. Yow, et al. (1979). “Failure of penicillin to eradicate group B streptococcal colonization in the pregnant woman. A couple study.” Am J Obstet Gynecol 135(8): 1062-1065. Click here.

17. Goldenberg, R. L., E. M. McClure, et al. (2006). “Use of vaginally administered chlorhexidine during labor to improve pregnancy outcomes.” Obstetrics and gynecology 107(5): 1139-1146. Click here.

18. Heath, P. T., G. F. Balfour, et al. (2009). “Group B streptococcal disease in infants: a case control study.” Arch Dis Child 94(9): 674-680. Click here.

19. Honest, H., S. Sharma, et al. (2006). “Rapid tests for group B Streptococcus colonization in laboring women: a systematic review.” Pediatrics 117(4): 1055-1066. Click here.

20. Johri, A. K., L. C. Paoletti, et al. (2006). “Group B Streptococcus: global incidence and vaccine development.” Nat Rev Microbiol 4(12): 932-942. Click here.

21. Kliegman, R. M., B. F. Stanton, et al. (2011). Nelson Textbook of Pediatrics, Saunders.

22. Libster, R., K. M. Edwards, et al. (2012). “Long-term outcomes of group B streptococcal meningitis.” Pediatrics 130(1): e8-15. Click here.

23. Mandell, G. L., J. E. Bennett, et al. (2010). Principles and practice of infectious diseases, Elsevier.

24. Matorras, R., A. Garcia-Perea, et al. (1991). “Maternal colonization by group B streptococci and puerperal infection; analysis of intrapartum chemoprophylaxis.” Eur J Obstet Gynecol Reprod Biol 38(3): 203-207. Click here.

25. Ohlsson, A. and V. S. Shah (2013). “Intrapartum antibiotics for known maternal Group B streptococcal colonization.” Cochrane Database Syst Rev 1: CD007467. Click here.

26. Ronnqvist, P.D., U. B. Forsgren-Brusk, et al. (2006). “Lactobacilli in the female genital tract in relation to other genital microbes and vaginal pH.” Acta Obstet Gynecol Scand 85(6): 726-735. Click here.

27. Schrag, S. J., E. R. Zell, et al. (2002). “A population-based comparison of strategies to prevent early-onset group B streptococcal disease in neonates.” N Engl J Med 347(4): 233-239. Click here.

28. Stade, B., V. Shah, et al. (2004). “Vaginal chlorhexidine during labour to prevent early-onset neonatal group B streptococcal infection.” Cochrane Database Syst Rev(3): CD003520. Click here.

29. Tudela, C. M., R. D. Stewart, et al. (2012). “Intrapartum evidence of early-onset group B streptococcus.” Obstetrics and gynecology 119(3): 626-629. Click here.

30. Tuppurainen, N. and M. Hallman (1989). “Prevention of neonatal group B streptococcal disease: intrapartum detection and chemoprophylaxis of heavily colonized parturients.” Obstetrics and gynecology 73(4): 583-587. Click here.

31. Valkenburg-van den Berg, A. W., A. J. Sprij, et al. (2009). “Association between colonization with Group B Streptococcus and preterm delivery: a systematic review.” Acta obstetricia et gynecologica Scandinavica 88(9): 958-967. Click here.

32. Van Dyke, M. K., C. R. Phares, et al. (2009). “Evaluation of universal antenatal screening for group B streptococcus.” N Engl J Med 360(25): 2626-2636. Click here.

33. Velaphi, S., J. D. Siegel, et al. (2003). “Early-onset group B streptococcal infection after a combined maternal and neonatal group B streptococcal chemoprophylaxis strategy.” Pediatrics 111(3): 541-547. Click here.

34. Weiss, M. E. and N. F. Adkinson (1988). “Immediate hypersensitivity reactions to penicillin and related antibiotics.” Clin Allergy 18(6): 515-540. Click here.

35. WHO. State of the art of vaccine research and development: Initiative for Vaccine Research. 2005. [online] http://www.who.int/vaccine_research/documents/Dip%20814.pdf.

36. Young, B. C., L. E. Dodge, et al. (2011). “Evaluation of a rapid, real-time intrapartum group B streptococcus assay.” Am J Obstet Gynecol 205(4): 372 e371-376. Click here.

37. Zarate, G. & Nader-Macias, M. E. (2006). “Influence of probiotic vaginal lactobacilli on in vitro adhesion of urogenital pathogens to vaginal epithelial cells.” Lett appl Microbiol 43(2): 174-178. Click here.


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