Group B streptococcus in pregnancy



Group B streptococcus (Streptococcus agalactiae or beta hemolytic streptococcus of group B) is one of the many bacteria present in the body where, normally, it does not cause any kind of problem. The person who "hosts" group B streptococcus (GBS) without disturbances (symptoms) it is indicated by the term "GBS carrier", or "colonized by GBS".

It has been estimated that approximately one in 4 pregnant women is a carrier or colonized by GBS, in the gastrointestinal and / or genitourinary tract.

When pregnant women are carriers of GBS, there is a risk that the bacterium will be passed on to the newborn while passing through the birth canal. While in most cases, colonization of the newborn does not result in disease, in rare cases GBS can cause invasive infections.

Streptococcus initially invades the blood through the respiratory tract or other mucous membranes of the body and, subsequently, spreads to other tissues manifesting itself as sepsis or with localized infections in certain organs or tissues (called focal) (bone, joint, soft tissue or of the urinary tract).


There are two types of neonatal GBS infection, distinguished by when symptoms develop: early infection, in which newborns develop infection within 7 days of birth, and late infection, with symptoms from 8 days up to 3 months of life.

In the case of early infection, most newborns show their first complaints (symptoms) as early as 12 hours after birth.
Disorders include:

  • low response to stimuli / lethargy
  • irritability
  • heart rate too high or too low
  • breathing rate too high or too low
  • altered temperature (high or low)

L'late infection it is often associated with meningitis, with possible permanent neurological damage. After the 3rd month, these types of infections are very rare. Often the initial complaints (symptoms) consist of fever and drowsiness, difficulty in sucking breast milk; seizures are rarely present in the initial phase, while later they can occur in about half of cases.


The Italian guideline on physiological pregnancy recommends the execution of a vaginal-rectal swab to all women at the 36th -37th week of pregnancy, looking for Group B beta-haemolytic streptococcus.
If the results show the presence of the bacterium (test positive), it is recommended that pregnant women be given antibiotic prophylaxis during delivery intravenously in order to stop the transmission of the bacterium from the mother to the newborn.

There are international guidelines which, in the absence of information on the state of colonization with GBS of the woman at the time of delivery, list the risk situations for the transmission of streptococcus from the mother to the newborn as indications for performing intrapartum antibiotic treatment:

  • preterm birth (<37 weeks of gestation)
  • fever of the parturient (> 38 ° C)
  • prolonged rupture of the amniotic membranes (> 18 hours)
  • previous child with neonatal GBS infection
  • bacteriuria (presence of GBS in the urine) during pregnancyto

These indications have been found to be valid in reducing early infections. However, fully effective preventive measures are not yet known to prevent late-onset infections.


Baldassari L (ed.). Group B streptococcal infectionsRome: Higher Institute of Health, 2007 (ISTISAN Reports 07/28)

Creti R (ed.). Early and late neonatal group B streptococcal infections in Italy. Rome: National Institute of Health, 2011 (ISTISAN Reports 11/7)

Physiological pregnancy guidelines 2011

Puopolo KM, Lynfield R, Cummings JJ, Committee on Fetus and Newborn, Committe on Infectious Diseases. Management of Infants at Risk for Group B Streptococcal Disease. Pediatrics. 2019; 144

In-depth link

NHS Choices. Group B Strep (English)

Centers for Disease Control and Prevention (CDC). Group B Strep (GBS) (English)

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