Group B Strep Testing

Posted in Pregnancy

asianpregnantGroup B streptococcus (GBS) is a bacterium that may be present in the rectum, vagina, or urinary tract of adults. It usually causes no symptoms in healthy adults. It is of concern when a pregnant person has it in their vagina because it can infect the baby and cause serious life-threatening respiratory complications. There are two main types of GBS infection in newborns: early infection and late infection. Here, I focus on early infection, which occurs in the first seven 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. Early infection is caused by direct transfer of GBS bacteria from the parent to the baby, usually after the water breaks. The bacteria travel up from the vagina into the amniotic fluid, where they may be swallowed into the lungs leading to 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.


Most GBS infections in newborns can be prevented by giving certain pregnant people intravenous antibiotics during labor. The Centers for Disease Control and Prevention (CDC) recommends intravenous antibiotics during labor for people with the following criteria:

  • A previous infant with invasive GBS disease
  • GBS in their urine in the current pregnancy
  • GBS+ culture result during the current pregnancy

The recommended treatment protocols for the above clinical situations are:

  • Penicillin G, 5 million units IV initial dose, then 2.5 million units IV every 4 hours until delivery OR
  • Ampicillin 2 grams IV initial dose, then 1 gram IV every 4 hours until delivery
  • If you are allergic to penicillin, the following antibiotics are used:
    • Clindamycin 900 mg IV every 8 hours until delivery OR
    • Erythromycin 500 mg IM (intramuscular) every 6 hours until delivery

The CDC also outlines who is at highest risk of having a baby with GBS infection. Those people at highest risk of having a baby with GBS infection have:

  • A fever during labor
  • Rupture of membranes (ROM) 18 hours or more before delivery
  • Labor or rupture of membranes before 37 weeks

People who do not have any of these criteria have a relatively low risk of delivering an infant with GBS disease.

The incidence of GBS infection in an otherwise healthy full term infant born to a GBS+ parent is 1-2% if antibiotics are not given during labor. The rate of infection drops to 0.2% if antibiotics are given during labor. The death rate from early GBS infection is 2-3% for otherwise healthy full term infants. This means of 100 babies who have an actual early GBS infection, 2-3 will die. Although the death rate of GBS is relatively low, infants with early GBS infections can have long, expensive stays in the intensive care unit.

The chance of the birthing parent experiencing a mild allergic reaction to penicillin (rash, hives) is 1 in 10 and the chance of developing a severe allergic reaction to penicillin (anaphylaxis) is 1 in 10,000. Anaphylaxis requires emergency treatment and can be life-threatening.


As mentioned above, some people are at higher risk of having a baby that becomes infected with GBS. In addition to the risk factors listed above, the following increase the chances of having a baby with GBS: African American race, multiple sexual partners, male-to-female oral sex, frequent or recent sex.

There are significant risks associated with antibiotic treatment, particularly antibiotic resistance in GBS and other bacteria, such as E. coli and MRSA. While the incidence of babies being infected by resistant organisms is low, each dose of antibiotics increases the overall chances of resistance developing. Antibiotics given to newborns also disrupt the normal colonization with their parent’s beneficial bacteria, thus increasing their risk of gastrointestinal distress and disease, allergies, and asthma, among other long-term health effects. It also allows other types of infectious bacteria to multiply, potentially creating the very risk for which you are being treated.


The incidence of GBS in newborns is based solely upon research done in hospitals, most of them large, tertiary care centers. Personalized and non-interventive care is not the norm in these settings. As of yet, there are no published rates derived from out-of-hospital births attended by midwives. This is significant because homebirths are associated with fewer vaginal interventions during labor, fewer maternal fevers, and less time between rupture of membranes and birth.

The standard of care emphasizing antibiotics for all GBS+ people does not address topics that are particularly pertinent to understanding why GBS infects certain babies and how therapies can be targeted more effectively.  For example, it is not known if antibodies to GBS are produced in breastmilk. It is not known whether pregnant parents produce antibodies to GBS that pass through the placenta. It is not known whether certain strains of GBS are more infectious than others.

I am concerned about the rise of antibiotic resistant organisms and the possible health consequences of antibiotic use. I feel that the current standard of care that recommends antibiotics to all GBS+ pregnant people (approximately 1.2 million each year) does not address the impact of obstetrical interventions on GBS infections, but does increase antibiotic resistance and health problems in individuals who receive antibiotics. I support the targeted use of antibiotics in the reduction of GBS infection in people with specific risk factors.

If transport to the hospital is needed, your GBS status is important to know. If you did not do a screening culture or if you are GBS positive, IV antibiotics during labor will be recommended. Additionally, your baby may be taken to the NICU for observation and/or a full sepsis workup. If you are GBS negative, hospital care providers will likely recognize that you do not need antibiotics and your baby does not need sepsis workups. Your postpartum time in the hospital will thus be shortened and unnecessary observation and testing on your baby will be avoided.



  • Decline GBS screening at 35-37 weeks of pregnancy
  • Accept GBS screening at 35-37 weeks of pregnancy
  • Receive antibiotics during labor if GBS+, regardless of the presence of risk factors
  • Receive antibiotics during labor if GBS+, only if risk factors are present
  • Decline antibiotics during labor if GBS+

If you choose not to screen or if you are GBS+ and decline antibiotics during labor, that is your right but you would not be following the standard recommendations for achieving a healthy pregnancy outcome. Make sure you talk to your healthcare provider about GBS screening and treatment before you reach 35 weeks gestation.