About Group B Strep

One more screening test was recently added to the roster of those routinely recommended during pregnancy. So what is your doctor or midwife looking for, and why is it important?

What is Group B Strep?
Group B strep (GBS) is a type of bacteria that lives in the bowel and/or vagina of approximately one in for women, says Renato Natale, associate chief of obstetrics at St. Joseph’s Hospital and London Health Sciences Centre and a professor at the University of Western Ontario. Usually, GBS doesn’t cause symptoms or problems.

What is GBS a concern during pregnancy?
GBS can be transmitted from mother to baby during birth, and if a newborn’s immature immune system can’t keep the bacteria in check, they can cause potentially life-threatening infections of the blood, lungs, or spinal fluid (meningitis). If a woman who is carrying GBS isn’t treated, the odds her baby will develop Group B strep disease is about one in 200. (About two-thirds of babies who develop GBS infections do so in the first week of life.) While premature babies are more likely to get sick than those born after 37 weeks, “because term babies make up the majority of babies being born, it’s nevertheless quite a large group of babies that can be affected,” notes Natale.

How can I tell if I carry GBS?
Swabs of the vagina and anus are collected and sent to the lab. Caregivers now recommend testing all expectant mothers for GBS between the 35th and 37th weeks of pregnancy.

What will happen if I test positive?
Your doctor or midwife will suggest you be given intravenous antibiotics when you go into labour. This strategy sharply reduces the odds of your baby developing a GBS infection: from about one in 200 to one in 4,000.

What if I get into labour before being tested?
Women who haven’t been tested are usually offered treatment during labour in situations that put babies at a higher-than-normal risk of developing GBS-related problems. That means if you develop a fever during labour, your labour lasts more than 18 hours, your waters break more than 18 hours before your baby’s birth, you’ve had an earlier urinary tract infection caused by GBS, you go into labour before 37 weeks, or you’ve had a previous baby with GBS disease, your doctor or midwife will recommend antibiotics.

Won’t such antibiotic use promote the evolution of drug-resistant bacteria?
True, scientists are concerned about antibiotic overuse for this reason. However, researchers are looking for alternatives: a London-based group will soon start studying whether giving women beneficial bacteria before labour can eliminate GBS from the reproductive tract.