Useful Information







Group B Strep (GBS)


Group B Streptococcus (or GBS) is a friendly bacteria living in some women's vaginas. It does not cause a concern provided that it does not infect the bladder, where it can cause a urinary tract infection. It can also be transmitted to the baby during birth.

If it is transmitted to the baby, the baby can develop GBS infection in the form of sepsis, pneumonia or meningitis. The overall incidence of infection is 1.8 per 1000 live births. Of those babies who develop the infection, the mortality rate is 5-9%. So it is a rare but serious infection in the newborn.

Since the 1990s, it appears that the incidence in infection has declined from 1.8 to 0.5 per 1000 live births due to prevention strategies.

There are certain factors that are thought to put babies at higher risk. These are if a woman:
  • had a previous infant with GBS infection
  • has had GBS bacteriuria (urinary infection) in this pregnancy
  • has positive GBS vaginal swab at 36 weeks



    Or risk factors that arise in labour:
  • preterm labour (before 37 weeks)
  • rupture of the amniotic membrane ("waters breaking") for more than 18 hours before delivery
  • temperature of the mother greater than 38C




Prevention of GBS infection in the newborn:
  • no strategy appears to prevent all infections in the newborn
  • presently, the recommendations from the Society of Obstetricians and Gynecologist of Canada (SOGC) is to treat women who are GBS positive or who have risk factors in labour using intravenous (iv) antibiotic for the duration of the labour.




Tests you will be offered:
  • urine screening test-if you are positive for GBS, you will be offered oral antibiotics to prevent the infection from spreading to your kidneys. For labour, you are considered to be-GBS positive and offered iv antibiotics.
  • vaginal swab at 36 weeks-if you are positive for GBS, you will be offered iv antibiotics in labour
  • if you develop risk factors, listed above (preterm labour, prolonged ruptured membranes, or a fever), you will be offered antibiotics in labour




How many women are GBS positive?

Probably 10-30% of women are GBS positive at 36 weeks.

How is the swab done?

At 36 weeks, you can do the swab on your own, in the bathroom in the clinic. It is like a Q-tip that you put into your vagina, you then take it out and run it back to touch your anus. This gives a sample from the inside and outside area of the birth canal.

How accurate are the results?

This is a major limitation of the strategy. Presently, if the woman is GBS negative at 36 weeks, there is a 10% chance she may be GBS positive by delivery. Or if she is GBS positive at 36 weeks, there is a 30% chance that she becomes GBS negative by delivery. Her status may actually change or the test was inaccurate the first time she did it. Screening is offered at 36-37 weeks because it takes two days for the lab to complete the test. We do the test early, so that if the woman goes into labour any time after that, we have the results-however, there is a chance that the results aren't accurate at the time of labour. There is research being done on a rapid test, which could be done at the time of labour.

What are the risks to the baby of not treating with iv antibiotics in labour if the woman is GBS positive?

We don't have all the information yet...and the management strategy still does not prevent infection in all newborns. Observational studies from 1984 included all babies born (preterm, very preterm, babies with concerns, and healthy babies), these studies showed that:

  • if you are GBS positive with no risk factors, the risk of infection to the baby is 1 in 200 live births
  • if you do have risk factors in addition to being GBS positive, the risk of infection to the baby is 1 in 25.
  • if you are GBS negative, and you do not have risk factors, the risk is 1 in 3200
  • if you are GBS negative and you do have risk factors, the risk is 1 in 1100.
These statistics are limited because they don't tell us what is the risk for just a group of healthy, term babies.


What is the follow-up for the baby if the woman is GBS positive?

Guidelines for care of the newborn have not been agreed upon yet. One suggested by the SOGC is that if the baby has no signs of infection, is more than 36 weeks gestation, and the woman received two doses of antibiotics in labour, there are no additional checks, tests or treatments needed. If the woman refuses antibiotics in labour, there is no suggested guideline for care of the newborn.

Which antibiotic is used, and what if I'm allergic to it?

Penicillin G (5 million units, then after every 4 hours, 2.5 million units) is the antibiotic most commonly prescribed by a physician. When ordering the vaginal swab test, the midwife will include the comment that you are allergic to Penicillin, and the lab will test the GBS (if present) for sensitivity to another antibiotic-such as, ampicillin, cefazolin, clindamycin, or erythromycin.

What if I'm planning a home birth and I'm GBS positive?

You can make a plan with your midwife. Being GBS positive does not make your labour high-risk and you can continue to plan for a home birth.

Do I have to have the iv hooked up the whole time I'm in labour? Can I get into the bath with the iv?

We usually run the antibiotics through the iv tubing, and then we can disconnect the tubing and attach a "lock" (it is a small plug in the iv site, at the woman's wrist). When the next dose is needed, usually 4 hours after the first, we reattach the tubing, run the antibiotics though, disconnect the tubing and reattach the "lock". The woman is free to roam around, get into and out of the bath as she likes.

What are the risks of taking the antibiotics?

The most common adverse effect of antibiotics is thrush. The antibiotics kill a lot of your friendly bacteria, leaving room for fungus, most commonly yeast, to take over. The woman can develop a yeast infection in her vagina, slowing healing of her perineum if she had a repair. Thrush can also take hold in the baby's mouth and in the woman's breast and nipples. Thrush can be treated and does not prevent a woman from breastfeeding. Some women take L. acidophilis, a probiotic sold in health food stores, to help restore their friendly bacteria as a preventative for thrush, or while treating for thrush.

Less common adverse effects of antibiotics are allergic reactions. Most common is itching and rash in response to the iv antibiotic. Less common, but most serious, is anaphylaxis in the woman (1 in 10 000) or in the baby (1 in 100 000) during labour.

The population risk is that 25% of women giving birth receive antibiotics. The risk of bacteria developing resistance and the evolution of "super-bugs" is a possible reality in the future.