Group Beta Streptococcus Testing
What is GBS?
Group B Streptococcus (GBS) is a type of bacteria that can cause illness in people of all ages. In newborns, GBS is a major cause of meningitis, pneumonia, and sepsis. Group B strep lives in the intestines and can migrate down to the rectum, vagina, and urinary tract. All around the world, anywhere from 10-30% of pregnant people are “colonized” with or carry GBS in their bodies. Using a swab of the rectum and vagina, people can test positive for GBS temporarily, on-and-off, or persistently. 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, GBS can cause infections in the newborn, and 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.
In the US, the CDC recommends testing everyone for GBS around 36 weeks. This is called universal testing. In some countries, a "wait and see" approach is used, where providers treat if there are signs of GBS. Testing is done via a vaginal and rectal swab, that can be done on yourself or by your midwives. There are risks of false negatives, in fact, up to 2/3 of early GBS infections in newborns have resulted from false negatives. In other words, you may be given a negative result when you do have GBS bacteria in your vagina. Often, babies who have early-onset GBS get sick within an hour of birth, indicating that they were exposed during the pregnancy, not the birth. Some moms prefer not to test for GBS and some moms prefer to test so they know if GBS is present.
What if I Test Positive?
If someone who carries GBS is not treated with antibiotics during labor, the baby’s risk of becoming colonized with GBS is approximately 50% and the risk of developing a serious, life-threatening GBS infection is 1% of that 50% of babies. As an important distinction, being colonized is not the same thing as having an early GBS infection– as we see statistically speaking, most colonized babies stay healthy.
Treatment for a Positive Test Result
The CDC recommends treating all moms who have a positive GBS result. The standard of care involves having IV antibiotics administered every 4 hours once the membranes rupture and/or during active labor. There are alternative treatments you can discuss with your midwifery team, although no alternatives are recommended by the CDC or ACOG.
Newborns at Higher Risk for Becoming Infected
- Being born at less than 37 weeks
- A long period between water breaking and giving birth
- Water broke before going into labor (premature rupture of membranes)
- High temperature during labor (> 99.5 F or 37.5 C)
- Infection of the uterus (aka “chorioamnionitis”)
Parent previously gave birth to an infant who had an early GBS infection
GBS in the urine during pregnancy
Intrauterine monitoring during labor
What are the Signs and Symptoms of GBS Infection?
Most babies who are infected with GBS show symptoms within 12 hours of birth. Part of our postpartum care is to monitor for signs of infection, and to encourage you to as well. This will include assessing your baby’s general wellbeing, feeding, temperature, heart rate and breathing rate. Babies with GBS infection may be very sleepy, be floppy and not feed well. Other symptoms can include grunting, a high or low temperature, abnormally fast or slow heart rate or breathing rate, irritability, low blood pressure, and low blood sugar.