Group B streptococcus (GBS) is one of many
bacteria that normally live in our bodies and usually cause no harm. This is called GBS carriage, colonization with GBS or carrying GBS.
When this infection occurs in the first week of a baby's life, it is known as early-onset GBS infection. Infections developing after the first week and up to three months of age (after which time GBS infection is extremely rare) are referred to as late-onset GBS infection. Late-onset GBS infection is not usually associated with the pregnancy and is not dealt with here.
Early-onset GBS infection
GBS infections can cause
blood poisoning (septicemia), infection of the
lung (pneumonia) or infection of the lining of the
brain (meningitis), and each of these can be life threatening. Sadly, even with the best medical care, 1 out of every 10 babies diagnosed with early-onset GBS infection will die.
However, if pregnancies at increased risk of GBS infection are identified and appropriately managed, most early-onset GBS disease in newborn babies could be prevented.
Identification of pregnancies at increased risk
Healthcare professionals are being encouraged to use clinical risk factors to identify pregnancies which are more likely to result in early-onset GBS infection.
Approximately 60% of cases of early-onset GBS infection are associated with these identifiable risk factors and it is likely that the majority of severely affected cases could be prevented by targeting this group.
Management of pregnancies at increased risk
antibiotics from the start of labor, and at intervals until delivery, are highly effective at reducing the risk of early-onset GBS infection in the baby. It is estimated that, with this preventive treatment, the risk of a baby developing early-onset GBS infection is reduced by approximately 90%.
The RCOG recommends the following approach to each risk factor:
- You have previously had a baby who had GBS infection - you should be offered
antibiotics during labor. If you carried GBS during a previous pregnancy and your baby did not develop a GBS infection, treatment during labor is not recommended.
- GBS has been found on
swabs from your vagina and/or rectum which have been taken for another reason- your healthcare professional should discuss the possibility of
antibiotic treatment during your labor with you. Treatment before labor or before your waters break does not reduce your chance of carrying GBS at the time of the birth.
- GBS has been found in your urine during your current pregnancy - you should be offered
antibiotics in labor after discussion with your healthcare professional.
- Your baby is at higher risk of developing GBS infection. This may be because you have a temperature of over 38C (100.4F) in labor, you go into preterm labor (before 37 completed weeks of pregnancy) or your waters have broken prematurely, or your waters have broken for more than 18 hours. In which case your healthcare professional should discuss with you the option of
antibiotic treatment during labor.
antibiotics are used in labor to reduce the risk of early-onset GBS infection, penicillin is usually given. Clindamycin is used as an alternative for those mothers
allergic to penicillin. You must inform the healthcare professional involved in your care if you have ever had an
allergic reaction to penicillin or any other
Antibiotic treatment is not recommended if you plan to have a
Caesarean and this takes place before labor begins and your waters have not yet broken.
Screening and testing for GBS in pregnancy
If you are offered a test to detect GBS carriage it is important that you understand the purpose of the test, are satisfied that it is relevant to your care and are clear about the implications of having a positive and negative result.
The most sensitive testing method requires
swabs to be taken from both your vagina and rectum, which are then processed in a laboratory in a special solution. This solution is referred to as an enriched culture medium.
GBS carriage can come and go, but a result from a sensitive test done a few weeks before delivery is relatively reliable at predicting whether or not you will carry GBS around the time of the birth. This does not mean that your baby will be affected.
When no other risk factors are present, about 1 in every 500 babies born to mothers with a positive test is likely to develop early-onset GBS infection. A negative test result, particularly if taken early in pregnancy or which has not used the sensitive method, does not guarantee that you will not be a carrier of GBS around the time of delivery.
After your baby is born
Most babies born to mothers who carry GBS are born healthy. If it is thought that a baby has a GBS infection, as opposed to being simply colonized with GBS, samples of the baby's
blood or fluid from the spinal cord can be tested. Healthy babies do not need tests for GBS or treatment.
Intensive care and
antibiotics successfully treat most babies with GBS infection, most of whom will make a full recovery.