Knowing the risk factors for group B strep colonization and disease is essential in helping prevent neonatal infections, guiding screening and treatment protocols, educating patients, and empowering people to reduce the burden of GBS-related disease. Being colonized with GBS does not mean you have an infection. However, invasive group B strep disease (iGBS) can occur when GBS causes an infection.
Risk Factors for GBS Colonization in Pregnant Individuals Include:
Modifiable Risk Factors:
  • Smoking
  • Maternal obesity
Nonmodifiable Risk Factors:
  • GBS-positive swab in a previous pregnancy
  • Previous baby with invasive GBS infection
  • Diabetes mellitus 
  • Of Black race
​
Some studies have also found these associations:
  • Being a healthcare worker
  • Infrequent handwashing (4 or fewer times a day)
  • Maternal age >36 years of age associated with persistent colonization
  • Maternal age >40 years of age
Learn more about colonization in nonpregnant individuals
Risk Factors in Babies Include:
​Prenatal-onset iGBS (Before birth):
  • Maternal GBS colonization: Maternal colonization is usually determined through a vaginal/rectal swab test during the 36th or 37th week of pregnancy. A positive GBS urine culture at any time during the pregnancy is a marker of heavy colonization.
  • Young maternal age
  • Of Black race

Other risk factors for prenatal-onset have not been well studied.
​Early-onset iGBS (Birth - 1 week): 
  • Maternal GBS colonization: The primary risk factor is maternal colonization. This is usually determined through a urine culture early in pregnancy or through a vaginal/rectal swab test during the 36th or 37th week of pregnancy.
  • GBS in Maternal Urine: The mother had GBS in their urine (bacteriuria) at any time during current pregnancy
  • Previous sibling with invasive GBS Disease: Mothers who have had a previous baby with early-onset GBS disease are at higher risk of transmitting GBS to subsequent babies.
  • Prolonged Rupture of Membranes: When the amniotic sac breaks more than 18 hours before delivery, there's an increased risk of GBS transmission. 
  • Fever During Labor: Maternal fever during labor can indicate infection, potentially linked to GBS transmission. 
  • Prematurity: Babies born before 37 weeks gestation are more susceptible.
  • Very low birth weight: Babies who weigh less than 1500 grams (3 lbs. 4.9 oz) at birth are at higher risk.
  • Intraamniotic infection
  • Young maternal age
  • Maternal black race​

​Note: Early-onset GBS disease is highly preventable with administration of maternal IV antibiotics during labor and delivery
​Late-onset iGBS (1 week - 3 months):
  • Maternal GBS colonization 
  • Intestinal colonization in the baby: GBS is present within the gut of the baby
  • Of black race
  • HIV infection
  • Prematurity: Babies born before 37 weeks gestation are more susceptible.
​Ultra late-onset iGBS (3 months +):
  • The risk factors of late-onset
  • Prematurity: Being born before 37 weeks gestation is significantly associated with ultra late-onset.
  • Immune deficiency
​Please note: GBS may reoccur. Recurrent GBS is when a baby has had a GBS infection, been treated successfully, and is later infected by GBS, again.
Protecting Against GBS
​Understanding these risk factors is crucial for prevention and early intervention. Screening for GBS during the 36th or 37th weeks of each pregnancy helps identify maternal carriers who will likely be GBS+ at the time of birth and gives the opportunity for those who are considered GBS+ to receive timely administration of IV antibiotics during labor and delivery to reduce the risk of early-onset GBS infection.
​Importance of Knowing Your Risk Factors
​By addressing risk factors which are modifiable or actionable, individuals and healthcare providers can take steps to potentially reduce the incidence of GBS colonization and subsequent infections. Being aware of all risk factors is an opportunity for patients and their healthcare providers to have important conversations to help guide pregnancy and newborn care.