Group B streptococcus and pregnancy

What is group B streptococcus?

Group B streptococcus (group B strep) is a common bacterium that is found in the body. It is usually harmless in adults. Up to 30 per cent of pregnant women carry the bacterium in their vagina or rectum. Sometimes, a woman who has group B strep can infect her baby during delivery. This can cause serious illness in the newborn. The mother may also become very ill from the infection after the delivery.

Facts about group B strep

Even if you have group B strep, your baby will not necessarily be infected or develop serious illness. Here are a few other facts about group B strep.

  • Group B strep is not a sexually transmitted disease (STD).
  • Group B strep is not the same as other types of streptococci bacteria, such as those that cause strep throat.
  • Often, group B strep causes no symptoms or problems in adults.
  • A mother who has group B strep can infect her newborn.
  • Group B strep may become a problem if you also have other risk factors during pregnancy.
  • When a mother with certain risk factors (see below) is treated for group B strep during delivery, the risk of her baby being infected or becoming seriously ill is much reduced.

What can increase the risk?

Certain risk factors during pregnancy can increase your chances of passing group B strep to your newborn. Here are some of those risk factors.

  • A urinary tract infection with group B strep.
  • Breaking or leaking of the amniotic sac (the bag of fluid that holds the baby) earlier than 37 weeks.
  • Labour earlier than 37 weeks.
  • The amniotic sac being broken for 18 hours or more before delivery.
  • Fever during labour.
  • You have had another baby with group B strep infection.

Treatment for group B strep

If your doctor or obstetrician thinks your baby is at risk of group B strep infection, you will be given an antibiotic to help stop the infection. The antibiotic is given through an intravenous line during labour and delivery.

If your baby becomes infected

If group B strep infects your baby, symptoms may take time to appear. Early-onset infection occurs within the first week of life, usually within a few hours of birth. Late-onset infections occur after the first week, usually within 90 days of birth. The baby may have infections in the blood, lungs, brain or spinal cord, or, more rarely, in a single, isolated spot such as a bone or joint. The infection will need prompt medical treatment.

Group B strep testing

The US Centers for Disease Control and Prevention and the Royal Australian and New Zealand College of Obstetricians and Gynaecologists recommend testing all women at 35-37 weeks of pregnancy. This involves using cotton swabs to take samples from the vagina and anus. The samples are then sent to a laboratory.

The results show whether you have group B strep bacteria in your genital area. These test results cannot say whether or not your baby will become infected with group B strep. They can, however, help your doctor or obstetrician decide whether treatment to prevent infection is needed. If the swabs show that you have group B strep bacteria in your genital area, treatment with antibiotics during labour is generally recommended.

Your pregnancy

If you carry group B strep there is a risk of your baby becoming infected during delivery, especially if other risk factors occur. However, you can be treated during labour and delivery. Ask your doctor or obstetrician any questions you have about group B strep.

Last Reviewed: 8 July 2009
myDr. Adapted from original material sourced from MediMedia.

References

1. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. College Statement: Screening and treatment for group B streptococcus in pregnancy [published 2007, July; accessed 2009, Jul 23]. Available at: http://www.ranzcog.edu.au/publications/statements/C-obs19.pdf
2. Centres for Disease Control and Prevention. Guidelines for GBS: summary [updated 2008, Apr 20; accessed 2009, Jul 24]. Available at: http://www.cdc.gov/groupbstrep/guidelines/summary.htm
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