What you need to know about Group B Streptococcus in Pregnancy

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Group B streptococcus (GBS), also known as group B strep, is one of many different bacteria which live inside your body. About a third of us has GBS in our gut without even knowing it. This bacteria is normally found in the vagina and/or rectum of about a quarter of women. If you do, you won’t know it’s there, as GBS doesn’t have any obvious symptoms.

GBS bacteria can be passed from you to your baby during labour but this doesn’t usually cause problems, and most women who carry GBS bacteria have healthy babies. It is thankfully only in rare cases that GBS can cause serious illness and, even more rarely, the loss of a newborn baby.

Though it’s unusual, GBS is the most common cause of severe infection in newborns, particularly in the first week after birth (early onset infection).  If you are carrying GBS, you won’t necessarily know, because there aren’t usually any ill-effects. There is a test available for GBS, but it’s not routinely carried out in pregnancy due to concerns about its reliability.

You may discover that you have GBS by chance, when you have a vaginal swab taken to check for something else. GBS test kits can be bought privately, but many experts don’t recommend these because GBS comes and goes, so a positive test early in your pregnancy doesn’t mean you’ll still have GBS at your baby’s birth and a negative test doesn’t necessarily mean you won’t have GBS at a later stage.
Among babies, there are 2 main types of group B strep disease.

  • Early-onset disease — occurs during the first week of life. The group B strep bacteria are passed from the mother to the baby, most often during labor and birth. Antibiotics given during labor can be very effective at preventing this transmission.
  • Late-onset disease — occurs from the first week through three months of life. This is sometimes due to passing of the bacteria from mother to newborn, but sometimes the bacteria come from another source. For a baby whose mother does not test positive for group B strep, the source of infection for late-onset disease can be hard to figure out and is often unknown.

Early-onset disease used to be the most common type of disease in babies. Today, because of effective early-onset disease prevention, early and late-onset disease occurs at similar low rates.

For early-onset disease, group B strep most commonly causes Sepsis (infection of the blood), Pneumonia (infection in the lungs), and sometimes Meningitis (infection of the fluid and lining around the brain). Similar illnesses are associated with late-onset group B strep disease. Meningitis is more common with late-onset group B strep disease than with early-onset group B strep disease.

For both early and late-onset group B strep disease, and particularly for babies who had meningitis, there may be long-term consequences of the group B strep infection such as deafness and developmental disabilities.

Risk Factors:

Some pregnant women are at higher risk of having a baby with early-onset disease. The factors that increase risk include:

  • Testing positive for group B strep late in the current pregnancy (35-37 weeks gestation)
  • Detecting group B strep in urine during the current pregnancy
  • Delivering early (before 37 weeks gestation)
  • Developing fever during labor
  • Having a long period between water breaking and delivering
  • Having a previous infant with early-onset disease
  • If you carry GBS in your vagina and/or rectum during your pregnancy.

Late-onset disease is more common among babies who are born prematurely (< 37 weeks). This is the strongest risk. Babies whose mothers tested group B strep positive also have a higher risk of late onset disease. The risk factors for late onset disease are not as well understood as for early-onset disease.

Most babies exposed to GBS before or during birth are healthy and suffer no ill-effects.  It isn’t clear why some babies develop an infection, while others don’t. What is clear is that most GBS infections in newborn babies can be prevented.
If you are in a high-risk group, you can have antibiotics via a drip that a doctor or nurse will put in a vein in your arm. This will be either from the start of your labour or from when your waters break, whichever comes first, and until your baby is born.

Caesareans are not recommended as a method of preventing GBS infection in babies. That’s because having a caesarean doesn’t eliminate the risk of GBS being passed on to your baby.  GBS may also cause you to have a uterus infection or urinary tract infection (UTI).

If you have been affected by GBS in a previous pregnancy, or are carrying it in your current pregnancy, talk to your midwife or obstetrician. You can then discuss a birth plan that includes steps to protect your baby from the infection.

If you have GBS in your current pregnancy, a hospital birth will be recommended, so you can have antibiotics if you need them.  Your pregnancy will then be managed so your baby is as protected as possible.

Women who are group B strep positive can breastfeed safely. There are many benefits for both the mother and child. Your baby is not at risk of catching GBS from breastfeeding, so there is no need to change your plans if you intend to breastfeed your baby.

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