Foothills Midwifery

Information on Group B Strep

What is Group B Strep (GBS)?

GBS is one of many common bacteria that live in the human body without causing harm in healthy people. GBS develops in the intestine from time to time, so sometimes it is present and sometimes it is not. GBS can be found in the intestine, rectum, and vagina in about 2 of every 10 pregnant women near the time of birth. GBS is NOT a sexually transmitted disease, and it does not cause discharge, itching, or other symptoms. This is not the same bacteria that causes Strep throat.

How Does GBS Cause Infection?

At the time of birth, babies are exposed to the GBS bacteria if it is present in the vagina. This can result in pneumonia or a blood infection. Full-term babies who are born to mothers who carry GBS in the vagina at the time of birth have a 1 in 200 chance of getting sick from GBS during the first few days after being born. Occasionally, moms can get a postpartum infection in the uterus also.

What are the risk factors?

Women are at higher risk for having a baby with a GBS infection if they: 

  • Start labour before they reach 37 weeks gestation.
  • Rupture their membranes (water breaks) more than 18 hours before giving birth.
  • If they have an unexplained fever during labour (38°C or higher). 
  • If they have already had a baby who had a GBS infection. 
  • If they have (or had) a bladder or kidney infection during pregnancy which was caused by the GBS bacteria.

Note- about 45% of GBS infections develop in infants of mothers without risk factors.

How Do You Know if You Have GBS?

Three to five weeks before your due date, during a regular prenatal visit, you or your midwife will collect a sample by touching the outer part of your vagina and the anus with a sterile Q-tip. It can then be determined if GBS bacteria grows in the culture that is sent to the lab from that Qtip sample.

How Can Infection from GBS Be Prevented?

If your GBS culture is positive within 5 weeks before you give birth, the standard of care in Calgary is that you be offered antibiotics during labor (SOGC). GBS is very sensitive to antibiotics and is easily removed from the vagina. A dose given up to 4 hours before birth reduces the chances of your baby from picking up the bacteria during the birth from 1 in 200 to 1 in 4000.

A review done by the Canadian Task Force on Preventative Health Care (2001) concluded that screening all women for GBS and only selectively using antibiotics for GBS positive women who had an additional risk factor, was a reasonable choice as well.

Although GBS is easy to remove from the vagina, it is not easy to remove from the intestine where it lives normally and without harm to you. GBS is not dangerous to you or your baby before birth, if you take antibiotics before you are in labor, GBS may return to the vagina from the intestine, as soon as you stop taking the medication.

How Will We Know if Your Baby Is Infected?

Babies who get sick from infection with GBS almost always do so in the first 24 hours after birth. Symptoms include difficult breathing (including grunting or having poor colour), problems maintaining temperature (too cold or too hot), or extreme sleepiness and poor feeding.

What Is the Treatment for a Baby with GBS Infection?

If the infection is caught early and your baby is full-term, most babies will completely recover with intravenous antibiotic treatment. Of the babies who get sick, about one in six can have serious complications. Some very seriously ill babies will die.

What If You Are Allergic to Penicillin?

Penicillin or a penicillin-type medication is the antibiotic recommended for preventing GBS infection. Women who carry GBS at the time of birth and who are allergic to penicillin can receive different antibiotics during labor. Be sure to tell your midwife if you are allergic to penicillin and what symptoms you had when you got that allergic reaction.


Research has shown that giving GBS positive mothers and/or mothers that present with risk factors, intravenous antibiotics during labour, can significantly reduce the frequency of GBS infection in the baby. Use of antibiotics in labour reduces the risk of infection from 1/200 for untreated mothers to 1/4000 when antibiotics are given at least 4 hours before the birth. Both treatment options will treat many women and babies unnecessarily and will miss some babies who really do need treatment. The increasing number of antibiotic resistant bacteria due to overuse of antibiotics is a global issue. Antibiotics can also cause or contribute to side-effects such as diarrhea, yeast infections, and allergic reactions. The challenge of GBS is one without an easy solution. We encourage you to read more about this topic and discuss any questions you have with us.


  • This document was adapted from “Share with Women” GBS document - Journal of Midwifery & Women’s health Vol 47 No 6 Nov/Dec 2002
  • Society of Obstetricians and Gynecologists of Canada JOGC Sept 2004 http:// pregnancy-groupb_e.asp
  • Shah, V. Ohlsson, - the Canadian Task Force on Preventative Heath Care. Prevention of Early Onset Group B Strep Infection in the Newborn: Systemic Review Recommendations. CTFPHC Technical Report #01-6 May, 2001 London, Ontario: Canadian Task Force. o Centers for Disease Control


Approved by the Division of Midwifery, Calgary Health Region, April, 2007