How Common Is Group B Strep in Pregnancy?

Group B streptococcus (GBS) is a bacterium that naturally lives in the digestive and reproductive systems. Although it’s not always harmful, GBS may lead to life-threatening infections when mothers pass the bacteria to their babies during childbirth.¹Liu Y, Ai H. Current research update on group B streptococcal infection related to obstetrics and gynecology. Front Pharmacol. 2024 Jun 17;15:1395673. https://doi.org/10.3389/fphar.2024.1395673

Knowing the prevalence and risks of GBS, pregnant women can make informed choices to protect their health and their baby’s well-being.

GBS rates in pregnancy

Group B strep is common in pregnancy, affecting 10 to 30 percent of expectant mothers.²Raabe VN, Shane AL. Group B streptococcus (streptococcus agalactiae). Microbiol Spectr. 2019 Mar;7(2). https://doi.org/10.1128/microbiolspec.GPP3-0007-2018 Routine testing in late pregnancy helps identify cases, and antibiotics during labor effectively reduce transmission risks.¹Liu Y, Ai H. Current research update on group B streptococcal infection related to obstetrics and gynecology. Front Pharmacol. 2024 Jun 17;15:1395673. https://doi.org/10.3389/fphar.2024.1395673

Despite its high prevalence, the presence of GBS bacteria does not necessarily indicate infection. Many women carry GBS without symptoms, and most newborns born to GBS–positive mothers are healthy.¹Liu Y, Ai H. Current research update on group B streptococcal infection related to obstetrics and gynecology. Front Pharmacol. 2024 Jun 17;15:1395673. https://doi.org/10.3389/fphar.2024.1395673

How often do babies get infected with GBS?

Some factors increase the likelihood of GBS transmission from mother to baby³Prevention of group B streptococcal early-onset disease in newborns: ACOG committee opinion, number 797. Obstet Gynecol. 2020 Feb;135(2):e51-e72. Erratum in: Obstet Gynecol. 2020 Apr;135(4):978-979. https://doi.org/10.1097/AOG.0000000000003824:

• Premature birth (before 37 weeks)
• Prolonged rupture of membranes (water breaking more than 18 hours before delivery)
• Low birth weight

While GBS colonization is common, only a small percentage of babies develop an infection. Without antibiotics, newborns’ risk of early onset GBS infection is 1 to 2 percent. However, proper antibiotic use during labor significantly reduces the risk.⁴Kristeva M, Tillman C, Goordeen A. Immunization against group B streptococci vs. intrapartum antibiotic prophylaxis in peripartum pregnant women and their neonates: a review. Cureus. 2017 Oct 13;9(10):e1775. https://doi.org/10.7759/cureus.1775

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GBS diagnosis and treatment

GBS colonization can change over time. A woman who tests negative early in pregnancy can become colonized later, and vice versa.

Testing is typically done late in the third trimester when results are most relevant for delivery, with GBS screenings between 36 and 37 weeks of pregnancy.³Prevention of group B streptococcal early-onset disease in newborns: ACOG committee opinion, number 797. Obstet Gynecol. 2020 Feb;135(2):e51-e72. Erratum in: Obstet Gynecol. 2020 Apr;135(4):978-979. https://doi.org/10.1097/AOG.0000000000003824 The test is a simple swab of the vagina and rectum, and results are available within a few days.

Women who test positive for GBS are given IV antibiotics during labor.⁴Kristeva M, Tillman C, Goordeen A. Immunization against group B streptococci vs. intrapartum antibiotic prophylaxis in peripartum pregnant women and their neonates: a review. Cureus. 2017 Oct 13;9(10):e1775. https://doi.org/10.7759/cureus.1775 Treating GBS before labor doesn’t prevent bacteria from regrowing.

Can you prevent GBS colonization?

There’s no sure way to prevent GBS since it’s a naturally occurring bacterium. However, a strong gut microbiome may protect against harmful invaders. Women can support GI and vaginal health through diet and supplements:

• Take probiotics that promote healthy vaginal and gut flora.⁵Menichini D, Chiossi G, Monari F, De Seta F, Facchinetti F. Supplementation of probiotics in pregnant women targeting group B streptococcus colonization: a systematic review and meta-analysis. Nutrients. 2022 Oct 27;14(21):4520. https://doi.org/10.3390/nu14214520
• Eat a low-sugar, high-fiber diet to prevent bacterial overgrowth.
• Supplement with vitamins and essential minerals to optimize immunity.
• Consume more antimicrobial foods like garlic and coconut oil.

Regular prenatal care, including timely GBS screening, is crucial for early detection and prevention. Taking the right precautions will help mothers minimize risks and support a safe, healthy pregnancy.

Footnotes

• 1
  Liu Y, Ai H. Current research update on group B streptococcal infection related to obstetrics and gynecology. Front Pharmacol. 2024 Jun 17;15:1395673. https://doi.org/10.3389/fphar.2024.1395673
• 2
  Raabe VN, Shane AL. Group B streptococcus (streptococcus agalactiae). Microbiol Spectr. 2019 Mar;7(2). https://doi.org/10.1128/microbiolspec.GPP3-0007-2018
• 3
  Prevention of group B streptococcal early-onset disease in newborns: ACOG committee opinion, number 797. Obstet Gynecol. 2020 Feb;135(2):e51-e72. Erratum in: Obstet Gynecol. 2020 Apr;135(4):978-979. https://doi.org/10.1097/AOG.0000000000003824
• 4
  Kristeva M, Tillman C, Goordeen A. Immunization against group B streptococci vs. intrapartum antibiotic prophylaxis in peripartum pregnant women and their neonates: a review. Cureus. 2017 Oct 13;9(10):e1775. https://doi.org/10.7759/cureus.1775
• 5
  Menichini D, Chiossi G, Monari F, De Seta F, Facchinetti F. Supplementation of probiotics in pregnant women targeting group B streptococcus colonization: a systematic review and meta-analysis. Nutrients. 2022 Oct 27;14(21):4520. https://doi.org/10.3390/nu14214520