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A Balancing Act With No Easy Solution: The Controversies of Treating All Pregnant Women for Group B Strep

Since 2002, The Centers for Disease Control (CDC) has recommended that doctors screen all pregnant women for Group B Strep between 35-37 weeks, and that all women who test positive receive IV antibiotics during labor.

This policy has more than halved the rate of early onset newborn GBS disease (GBS infection occurring within the first week of life).

But the policy remains controversial, largely because it requires that thousands of healthy laboring women receive antibiotics to prevent a single infant death.

What is GBS?


    Group B Strep (GBS) bacteria are a normal part of the gut flora.

    It is not an STD and is not sexually transmitted.

    An estimated 1 in 4 pregnant women in the U.S. carry GBS bacteria in their digestive and reproductive tracts.


    Although generally harmless, GBS can cause serious disease in people with compromised immune systems, including newborns.


    Without IV antibiotics, about half of pregnant women colonized with GBS will pass the bacteria on to their babies during labor.

    About 1 in 100 exposed newborns will become seriously ill–developing sepsis, meningitis, and pneumonia.

    Of those who become ill, 1 in 20 will die.


    For more background on GBS, pregnancy, and delivery, check out our GBS Q&A.


    Read more


A Brief History of GBS prevention strategies in the United States

Hospitals in the U.S. began using IV antibiotics during labor to prevent GBS disease in the 1990s. Before then, GBS caused serious illness in over 7,000 infants and led to over 300 infant deaths each year. Eighty percent of the infants who died were less than 7 days old.

Initially, hospitals could choose one of two approaches for identifying who was at risk of passing GBS on to their babies and should therefore receive IV antibiotics:

1. A Risk-based Approach: Only women considered at high risk receive antibioticsWomen were at high risk if they…

  • had GBS in the urine at any point during their pregnancy
  • previously gave birth to an infant with a GBS infection
  • went into preterm labor at less than 37 weeks
  • ran a fever during labor
  • their water had been broken for more than 18 hours.

(The UK and several other developed nations continue to use a risk-based approach.)

  • A Universal Screening Approach: All pregnant women between 35 and 37 weeks are screened for GBS. Anyone who tests positive receives IV antibiotics during labor.

These policies led to a 65% drop in early onset GBS disease, from 1-2 in 1000 infants to less than 1 in 2,000 infants.


Then, in 2002, a large study found that, compared with a risk-based approach, the universal screening approach cut the risk of early onset GBS disease in half.

In response, the CDC updated their guidelines to mandate a universal screening approach. Now all pregnant women in the U.S. are screened between 35 and 37 weeks, unless already known to be GBS positive. Any woman testing positive must receive IV antibiotics during labor.

Public health officials credit widespread universal screening with a further drop in GBS disease from 47 infants in 100,000 to 34 infants in 100,000. Since the initial switch, the rate of early onset GBS infections has continued to fall, dropping from 37 in 100,000 (in 2006) to 23 in 100,000 (in 2015).  

Yet, despite the apparent success of universal screening, it remains controversial. For good reason…

Widespread exposure to antibiotics

Universal screening means many, many women receive antibiotics, even though their babies would never have become ill. To put some numbers to this problem,  in the U.S., about 30% of all laboring women receive IV antibiotics for GBS. The United Kingdom’s Royal College of Obstetricians and Gynecologists estimated that doctors have to screen 24,000 pregnant women and treat 7000 laboring women with antibiotics to prevent a single infant death.

Is it worth it?

The trade-offs here are complex.

If we lived in a vacuum, if our only concern was reducing the risk of GBS disease, then every laboring woman should receive IV antibiotics. After all, screening is imperfect. GBS colonization can fluctuate. Some women become positive after screening negative. And babies born to these women account for half of recent cases of early onset GBS.

So if we are willing to treat a third of all laboring women, why not treat all of them

Answer: Because of the risks of antibiotics.

The potential risks of antibiotics during labor

Several studies have linked IV antibiotics with an rise in antibiotic-resistant bacteria, including antibiotic resistant E. coli. An estimated 20% of GBS is now resistant to clindamycin, a common alternative to penicillin.

IV antibiotics also disrupt the normal seeding of the newborn gut microbiome (the diverse bacterial community living in our intestines).

This last problem, disruption of the infant gut microbiome, is an increasing source of concern.

Delivery and the newborn gut microbiome

During a vaginal labor and delivery, mothers pass their gut bacteria to their babies. Being coated in their mother’s gut, skin, and vaginal bacteria seeds the new baby’s own microbiome.

The prep for this event begins during pregnancy. Pregnant women’s bodies cultivate specific bacterial species while pruning out others. Bacterial communities in a woman’s vagina and nipples decrease in diversity and shift towards the suite of bacteria commonly found in newborns’ guts, such as Bifidobacteria, Lactobacilli, Staphylococcus, Enterococcus, and Streptococcus.

What do these bacteria do for babies?

Gut bacteria help maintain the lining of the gut, preventing infection. They allow babies to break down otherwise indigestible food, including human milk oligosaccharides (HMOs), a type of carbohydrate found exclusively in breastmilk. And they provide essential vitamins our bodies cannot generate on their own.

But perhaps most importantly, these bacteria help train the infant immune system to distinguish self from other, and pathogen from passerby.

Many scientists believe disrupting the infant microbiome could raise children’s risk of asthma, allergies, and autoimmune disorders, such as Crohn’s Disease, Type 1 Diabetes, and Multiple Sclerosis. As medical procedures like C-sections and IV antibiotics for GBS have become commonplace, we have witnessed a dramatic rise in the incidence of autoimmune diseases and allergies and asthma.

Bringing it back to GBS…

Nearly half of all women in the US currently receive antibiotics during labor. This is tantamount to an enormous, nationwide study on the importance of the infant microbiome.

For every newborn’s life saved, we could be raising thousands of children’s risk for asthma, allergies, autoimmune disorders, and obesity.


Hope for better solutions: New GBS guidelines coming soon.

New national guidelines on GBS are slated for release in 2019. The American College of Obstetricians and Gynecologists will take over the maternal component of these guidelines from the CDC. The American Academy of Pediatrics will take over the newborn component.

This could signal a change. The AAP recently issued a statement emphasizing the risks of widespread antibiotic administration (Hallelujah!)—

“The intent of such practice is to keep newborns safe. However, the unintended consequences… may manifest as increased risks of death, necrotizing enterocolitis and chronic lung disease among very preterm infants, as well as negative impacts on exclusive breastfeeding and increased risks of early childhood atopic diseases.”

But more than better policies, what we really need is better solutions.

The better way out of this dilemma? Better solutions. Like a vaccine.

A vaccine for GBS has been a top priority since the 1980s. An effective GBS vaccine would not only remove the need for IV antibiotics during labor. It could also reduce the rate of late onset GBS disease, which we cannot currently prevent. A vaccine could also help prevent pregnancy complications linked with GBS, including some preterm labors and stillbirths. And a vaccine would be a godsend in the developing world, where many women lack access to adequate prenatal care.

A few companies now have candidate vaccines that are finally entering human trials–but these are still likely years from release.

In the meantime, what can you do to avoid antibiotics?

If you test positive for GBS in the U.S., you are virtually assured to receive antibiotics during labor.

Thus your best hope is to not test positive in this first place. To prevent testing positive, many women turn to natural remedies (yogurt squatting, anyone?). We dig into the evidence about these not for-the-squeamish ways to get rid of GBS.


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About Amy

Amy Kiefer is a researcher by training, and earned her Ph.D. from the University of Michigan. She currently lives in the Bay Area with her husband and three children where she writes about fertility, pregnancy, and breastfeeding. Check out her blog,, for more great evidence-based pregnancy and parenting info.


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