Prevent Prenatal Infection: Learn About Group B Strep

February is Prenatal Infection Prevention Awareness month. A prenatal infection is any kind of infection you can get during pregnancy, but most importantly, the ones that can cause serious health problems for you and your baby. Some prenatal infections that can cause harm include:

  • Bacterial vaginosis
  • Chlamydia
  • Cytomegalovirus (CMV)
  • Fifth disease
  • Untreated gonorrhea
  • Group B streptococcus (GBS, group B strep)
  • Genital herpes (infected late in pregnancy)
  • Hepatitis B virus (HBV)
  • Hepatitis C virus (HCV)
  • Human papillomavirus (HPV)
  • Listeria/listeriosis
  • Rubella
  • Syphilis
  • Toxoplasmosis
  • Trichomonoiasis
  • Zika virus

In this post, we're going to talk about Group B strep. Whether or not you have it, the term Group B strep and its prenatal testing is something that almost every pregnant person comes in contact with during pregnancy. Later this month, we'll touch on two other common prenatal infections - cytomegalovirus (CMV) and bacterial vaginosis (BV).

What Is Group B Strep?

group b strep.pngGroup B strep -- otherwise known as GBS or group B streptococcus -- is a common bacterial infection in the vagina or rectum that is present in about 1 out of 4 adult women, including those who are pregnant. (GBS also occurs in men.) GBS in adults does not present as a typical infection -- most who have it are healthy, don't know they have it, do not show any symptoms, and do not require treatment to get rid of it. Group B strep in newborns, however, can cause group B strep disease, a serious and risky illness that can be passed to a newborn during birth (vaginal and cesarean, if water has been broken), which is why when group B strep is detected during pregnancy, it is treated in labor.

The Test

Most all pregnant people, late in the third trimester between weeks 35-37, will be tested for group B strep, as is recommended by the Centers for Disease Control (CDC) and the American College of Obstetricians and Gynecologists (ACOG). The test, which is called a "culture" is performed by a midwife or obstetrician using a long cotton swab that collects bacteria first from the vagina (2cm inside) and then the rectum (1cm inside). It is a quick and usually painless procedure. The swab is sent out to grow the culture in a lab to determine if GBS is present. You will likely receive the results from your test during your next prenatal visit, or within a few days by calling into the office or checking the online health portal. 

Positive Results

If your results from the group B strep test come back positive, your pregnancy is labeled "GBS positive." Treatment will not be prescribed during pregnancy to get rid of group B strep. This is due to the fact that even if you take antibiotics to get rid of group B strep during pregnancy, the bacteria can appear again by the time you give birth. It takes 1-3 days for GBS culture to grow in the standard testing, and there is currently not an effective and reliable quick GBS test widely available while in labor (researchers have evaluated quicker tests, which are being used currently in some countries). Since labor and birth can range from a few hours to a few days, this does not present a reliable way of receiving results before birth. 

Given these issues surrounding the nature of group B strep, the most effective way to treat it and prevent its transmission to the newborn, is for the pregnant person to receive antibiotics during labor.


If you have tested positive for GBS, you will receive antibiotics (penicillin, unless there is an allergy) during labor. Antibiotics are administered by IV at least four hours before birth is expected, and repeated every four hours. If you have a planned cesarean, you will not need antibiotics unless your water has broken. 

Your Baby

If you tested positive for GBS, and you were treated as recommended in labor for it, your baby has a low chance of contracting group B strep disease as a newborn and will likely not need any special testing or treatment. If you had a uterine infection, however, your baby should be tested after birth for GBS.  

If you tested positive for GBS and you were not treated with antibiotics during labor, your baby will likely not need special testing but will be observed closely for 48 hours (separation from parents is not necessary for this kind of observation). Babies born to parents with group B strep who are not treated in labor have a 1-2% chance of contracting GBS.  

There are special circumstances that make a GBS infection more likely in infants, like if you are GBS positive and have: preterm birth, broken water for more than 18 hours before birth, fever during labor, a previous baby with GBS infection, and a urinary tract infection (UTI) during pregnancy that was caused by GBS.

There are two types of group B strep infection in newborns -- early onset and late onset. Early onset GBS in infants occurs in the first seven days and symptoms usually start on the first day. Symptoms of early onset group B strep include fever, breathing problems, drowsiness, and heart and blood pressure instability. Early onset GBS can cause pneumonia, sepsis, or meningitis. Late onset GBS in infants shows up from 7 days to 3 months and symptoms are coughing or congestion, fever, eating problems, drowsiness, or seizures. Late onset group B strep is less common than early onset, and also can cause sepsis and meningitis. If group B strep is detected in babies, it is treated through IV antibiotics. 

Alternative Remedies

Research has shown that the best treatment for GBS in babies is through prevention, by treating GBS in parents through antibiotics. While there are several alternative remedies that have been tried and recommended anecdotally, none have been shown through research to be effective. If you would like to learn more about these and what the research says, I encourage you to read through the evidence on group B strep at Evidence Based Birth.  

For more in depth information and questions on group B strep in adults and infants, check out the comprehensive resources found at CDC and ACOG



National Institute of Child Health and Development, "What Infections Can Affect Pregnancy?"

American Pregnancy, "Group B Strep Infection: GBS,"

Centers for Disease Control and Prevention, "Group B Strep (GBS),"

Mayo Clinic, "Group B Strep Disease,"

American College of Obstetricians and Gynecologists, "FAQ: Group B Strep and Pregnancy,"

March of Dimes, "Group B Strep Infection,"

Evidence Based Birth, "Evidence on: Group B Strep in Pregnancy,"

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