Group B Streptococcus in Pregnancy
Group B Streptococcus, also known as GBS, is a common bacterium that inhabits the lower gastrointestinal tract in about 20% to 30% of the population. In women, it can also spread to the urinary tract and the vagina, but in most cases it does not cause problems or infections. However, during pregnancy the bacterium can cause urinary tract infections and preterm birth, and during labor it can cause a life-threatening infection in the newborn.
Transmission of the bacterium from the mother to the newborn during labor occurs when the baby passes through the birth canal or as a result of swallowing amniotic fluid containing the bacterium into the lungs. After rupture of membranes, the bacterium can pass from the vagina into the uterus and the amniotic fluid.
Important note
Important note
This article addresses Group B Streptococcus and not Group A Streptococcus, which can cause several diseases such as strep throat, scarlet fever, impetigo, and others.
Implications of infection in the newborn
A baby who becomes infected with Group B Streptococcus may develop illness, usually during the first week of life, with symptoms appearing in most cases within the first 12 to 48 hours after birth. The initial symptoms resemble pneumonia and may progress to meningitis, which can cause long term neurodevelopmental impairment, and to bloodstream infection (sepsis), which may be fatal.
The risk of death in full term infants who become infected and develop the disease is estimated at about 8% to 17%. In preterm infants born before week 33, the risk is three times higher.
Risk of transmission to the newborn
In a pregnant woman who is a carrier and does not receive antibiotic treatment before delivery, the risk of transmitting Group B Streptococcus to the newborn is 50%, of whom 1% to 2% will develop a life-threatening illness.
Since this is a bacterium and not a virus, the treatment is antibiotic therapy. The simplest antibiotic, penicillin, is effective against Group B Streptococcus and is therefore the treatment of choice.
If the mother receives antibiotic treatment during labor, the risk of disease in the newborn is reduced by about 80%.
Screening test for prevention and early treatment
Since antibiotic treatment during labor has been found to be effective in reducing the risk of infection in the newborn, the Ministry of Health decided to add, as of December 2023, a new screening test for detecting carriage of Group B Streptococcus (GBS test) to routine pregnancy follow up.
Timing of the test
From the beginning of week 36 until the end of week 37 of pregnancy.
How the test is performed
A swab is taken using a cotton swab from the vaginal opening and from the rectal opening. The swab is sent to a laboratory for culture.
How to perform the test
You should ask your treating physician for a referral for the test, obtain the appropriate swab from your health maintenance organization, and perform the swab independently at home. After performing the test, it is important to make sure to deliver the swab to the health maintenance organization laboratory within 24 hours. Until delivery, the sample can be kept at room temperature.
Important note
Important note
If during pregnancy you were diagnosed with a positive urine culture for Group B Streptococcus, or if you have a history of delivering a baby who became ill with this bacterium, you may forgo the screening test, as the recommendation is to administer preventive antibiotic treatment during labor in any case.
Guidelines upon arrival for labor
If you have performed the GBS screening test, it is important to remember to bring the test result with you to the delivery room. If the test shows that you are positive, you will receive antibiotic treatment as soon as possible after rupture of membranes or the onset of regular contractions.
If you arrive at the delivery room without knowing whether you are a carrier, you will receive preventive treatment during labor if one of the following risk factors is present:
- A previous preterm birth before week 37+0.
- A fever of 38°C or higher during labor.
- Rupture of membranes lasting 18 hours or more.
In case of a positive GBS result on a rapid test performed in the delivery room (if the test is available and time allows). If a negative result is obtained on the rapid test, the physician may decide to forgo antibiotic administration even in cases of preterm labor or rupture of membranes lasting more than 18 hours.