At your 35-37 week visit, a rectal culture will be performed by your provider. This culture detects the presence of a bacteria called Group B Streptococcus (GBS).
Approximately 15% of pregnant women will have colonizing Group B strep bacteria. The vast majority of these women have no symptoms of infection. Generally, outside of pregnancy, this bacteria causes very few problems.
Why is it important to detect GBS during pregnancy?
It is important to detect GBS because approximately 11/1,000 infants born to mothers carrying the bacteria will become infected during labor. Certain factors such as prematurity, fever in labor, and prolonged rupture of the bag or amniotic membranes can increase this risk. Newborn infants have very little immunity to this bacteria and a substantial proportion of those who contract the infection at birth can become severely ill, with the dominant problem being pneumonia and/or meningitis.
What if the screen is positive?
Those who are found to have a positive GBS screen will be offered antibiotic therapy in labor. Penicillin or Ampicillin is general administered intravenously every four to six hours, once the membranes have been ruptured, or once active labor has begun. The antibiotics are discontinued once Baby has been delivered. If you are allergic to Penicillin, then an alternative antibiotic will be used. The antibiotics given are able to cross the placenta and deliver immunity to the baby within 30 minutes. Cesarean section is not recommended as a way to prevent GBS infections, since antibiotic treatment is much simpler and extremely effective.