It is standard of care that all pregnant women get screened for Group B Streptococcus (GBS).  The recommended time to get screened by your primary care provider is between 36 weeks and 37 weeks 6 days of gestation.  Even women who are having a planned Caesarian section will likely be screened.

How is Screening Done?

Screening for GBS is completed by the primary care provider during a routine prenatal appointment.  The lower vagina and the rectum are swabbed.  These swabs are sent to a lab to test for GBS.

GBS is a leading cause of newborn infections

GBS colonizes up to 30% of pregnant women.  Colonization does not mean the mother is infected, it means she is carrying the bacteria and has no symptoms of infection.

These bacteria can be transferred to a baby during delivery after the onset of labor or rupture of membranes.  They can also transfer when the baby passes through the birth canal. 

GBS Early-Onset Disease

Babies are born with very low immunity and are at a high risk for infection.  GBS screening is done to prevent GBS early-onset disease (EOD) in a newborn baby.  This is an infection that occurs within 7 days of the baby being born.

Most GBS EOD in newborn babies present as:

  • Sepsis
  • Pneumonia (lung infection) or
  • Meningitis (infection in brain or spinal cord) which is more rare

Preventing GBS EOD

If a pregnant woman has had a positive GBS screen, she will receive intravenous antibiotics during labor

Most newborn babies with GBS EOD will show symptoms within 24 hours of birth.  Nurses and physicians will monitor infants closely during this time.  

Parents will be counseled about the signs and symptoms of GBS EOD in their newborn baby if they are discharged home before 48 hours of life.  

This post was co-authored by Stephanie Liu, MD, MSc, CCFP, BHSc and Erin Manchuk, BScPharm, BCGP .