EP 8: What is Group B Strep (GBS) ?

Group B strep is a bacteria that can cause illness in some people. It is NOT AN STD and it is not strep throat. GBS lives in the intestines and can migrates down to the rectum, vagina, and urinary tract. 10-30% of pregnant people are “colonized” with or carry GBS. Being colonized with GBS does not mean that someone will develop a GBS infection. Most people with GBS do not have any GBS infections or symptoms, however a mother colonized with GBS poses a risk for infection in the newborn from birth. People who have preterm births are 1.7 times more likely to be colonized with GBS during labor than people who do not have preterm births.

  • Most newborns birthed from a mother who is GBS positive (meaning she is a carrier/is colonized) do absolutely perfect and present with NO infection.

  • In newborns who do develop an infection from GBS, it 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).

  • It is also important to know that people can test positive for GBS temporarily, on-and-off, or persistently.

  • A pregnant women in the U.S. is tested for GBS using a swab of the rectum and vagina. You will be tested at 35-37 weeks. Swab and see if it grows, it usually takes 48 hrs and is semi accurate because : women who were negative for GBS at 35-36 weeks, 91% were still GBS-negative when the gold standard test was done (tested during labor). The other 9% became GBS positive. These 9% were “missed” GBS cases, these women did not get the antibiotics needed.

  • Women who screened positive for GBS at 35-36 weeks, only 84% were still GBS positive when the gold standard test was done during labor. However, 16% of the GBS-positive people became GBS-negative by the time they went into labor and were treating with antibiotics they did not need.

  • In the real world we would love to test upon going into labor, it would be the most accurate. HOWEVER most of the time we don't have 48 hours to wait on results because most women are not in labor that long.

  • Newborn infection: Most infection is within the first 7 days of life with symptoms beginning around 12 hrs old. If symptoms are detected within 1 hr of birth it is suggesting infection happened before birth. Infection happens after water breaks and bacteria travels up into amniotic fluid.

  • Solution/ treatment for GBS: intrapartum (during labor) IV antibiotics every 4 hours (Ancef is commonly used). This decreases chances of infant infection after the mother has had at least 2 doses. This does not mean you have to stay connected to your IV the entire time if you're desiring a natural labor and want to move around, the antibiotic takes about 15-30minutes to infuse only. Your temperature will be checked every hour once your water broken if you are GBS positive, that way if you spike a temperature it is caught quickly. If your GBS status is unknown (no prenatal care or preterm labor before getting tested) most hospitals will treat you like you are positive with antibiotics.

  • 0.25 cases per 1,000 births today result in infant GBS infection. If you are GBS positive and do not receive antibiotics the risk of infant developing a serious, life-threatening GBS infection is 1 to 2%. Antibiotics drop infant infection rate by 80% from %1 to 0.2%.

  • "Uruguay in 2015 followed 60 carriers of GBS at term who came to the hospital in early labor. They swabbed each person for GBS before antibiotics were started, and then again 2 and 4 hours after the first dose of penicillin was given. The researchers found that 72% of the participants were GBS positive before antibiotics were started, 47% were positive 2 hours after the first dose, and only 12% were positive for GBS 4 hours after the first dose" (Dekker, 2017).

  • "Seven of eight studies found that IV antibiotics during labor had at least a short-term effect on reducing beneficial bacteria and/or increasing levels of non-beneficial bacteria. Of the four studies that followed the infant microbiome over time, two found that the infant’s microbiome had either recovered or mostly recovered by 4-8 weeks, while two other studies found important differences that persisted up to 3 months or a year later in some infants. IV antibiotics during labor have a short-term negative effect on the infant’s microbiome, but that this negative effect can be lessened by breastfeeding" (Dekker, 2017).

  • Risk factors for infant GBS infection: mother must have positive GBS, preterm birth (<37 weeks), prolonged water rupture to delivery, PROM (premature rupture, water broke before labor), maternal fever in labor, chorioamnionitis, internal monitoring during labor, previous infant with infection, and first time birth.


  • Garlic + GBS in pietri dish did kill it at about 3hrs. So by temporarily using garlic, this could help you get a negative test result, but the effect may wear off very quickly.

  • researchers randomly assigned 110 women in Taiwan who were GBS positive at 35-37 weeks to take either two probiotic capsules each night at bedtime, or two placebo capsules. treatment for each person lasted 3 weeks on average, GBS culture test was repeated when women returned to the hospital to give birth. 43% of GBS positive people who took probiotics were GBS negative when they went into labor, compared to 14% in the placebo group. probiotics show promise for GBS prevention during pregnancy and birth.

  • Increase chances of maternal carrier of GBS: Multiple sexual partners, Male-to-female oral sex, Frequent or recent sex, Tampon use, Infrequent handwashing, Less than 20 years old


Dekker, R. (2017, July 17). Evidence on group b strep in pregnancy. Retrieved February 04, 2021, from https://evidencebasedbirth.com/groupbstrep/

ACOG - Group b strep and pregnancy. (2019, July). Retrieved February 04, 2021, from https://www.acog.org/womens-health/faqs/group-b-strep-and-pregnancy