What to expect if you test GBS positive

During pregnancy, your OB or midwife will discuss Group B streptococcus (GBS) screening with you. Here’s what you need to know if you're GBS positive.

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With my second child, my water broke two weeks early, at 10 p.m., when my partner was out of town. After phoning our babysitter to tell her it was go time, I called my closest friend. Within 15 minutes she was at my house, editing the contents of my hospital bag, pausing to make fun of me for packing a novel and ensuring I had a decent outfit to come home in. She also ran down the list of “what to do if you’re in labour” questions on the handout from my doctor, which I’d dutifully stuck on the fridge. “Are you strep B positive?” she asked.

When I said yes, she whisked me into her car and sped toward the hospital. I was hustled into a bed, where the nurse popped an IV full of strep-fighting antibiotics into my arm. Twelve hours later, my healthy baby boy was born, safe and sound.

Most pregnant women are tested for Group B streptococcus (GBS), a type of bacteria found in the vagina or rectum that can be passed on to the baby during delivery. Knowing whether you are GBS-positive or GBS-negative will help you put together your birth plan. It’s estimated that 10 to 30 percent of North American women are carriers.

“The bacteria colonizes the lower digestive tract and vagina, and has little or no effect on the pregnant mother. But if it shows up at 35 weeks, it means the bacteria is active, and you’ll automatically be given antibiotics during labour,” says Beverley Jackson, a family doctor in Toronto.

While most babies aren’t affected by GBS, a very small number (one to two percent) will develop an early-onset infection that can attack their blood, brain, lungs and spinal cord.

“There’s no rhyme or reason for who gets it,” says Noor Ladhani, a maternal fetal medicine specialist at Sunnybrook Hospital in Toronto. “And the aftermath of an untreated infection can, in rare cases, be devastating.”

How do you know if you have GBS?

This depends on your care provider. Many midwives will give you a choice as to whether you want to be checked for it at all, whereas if you have an OB, it’s a standard screening. Early in pregnancy, your urine is tested for infections. Women who don’t show a positive result then are tested again at 35 to 37 weeks—this time, by a swab of the vagina and rectum—because GBS can come and go during pregnancy. (Some OBs and midwives allow women to go to the washroom and do their own swabs.)

Is the group B strep test optional?

There are different guidelines for GBS screening, says CJ Blennerhassett, a registered midwife with Kensington Midwives in Toronto. In the protocol outlined by the Association of Ontario Midwives, for example, “there’s choice around whether to screen at all, and choice around what you do with that information,” she says. Some midwives and pregnant women believe administering what’s called “prophylactic” antibiotics is a very broad-strokes measure. If you are GBS-positive, there is a one in 200 chance your infant will develop an infection. (With intravenous antibiotics—usually penicillin—the chances decrease to one in 4,000.) Some patients choose to forgo the preventive antibiotics due to concerns about overprescribing and the rise of antibiotic resistance. Another reason, says Blennerhassett, is that we now value the role of bacteria in infant gut health, and some women would prefer not to wipe out all the good gut bacteria during delivery.

Discuss your options with your midwife. At some hospitals, a midwifery patient who’s labelled “GBS unknown” will still be treated as if she’s GBS-positive, says Blennerhassett. At others, staff will treat a woman who has not been tested for GBS as negative, unless she is showing additional risk factors during labour (such as fever or signs of infection), or if it’s been 18 hours since her water broke.

Will taking antibiotics during labour change your birth plan?

If you find out you’re GBS-positive, ask your OB or midwife about how the antibiotics will be administered. “It doesn’t impede mobility too much,” says Blennerhassett. “You might have an IV lock in your hand, but you’re only hooked up for the 15 to 30 minutes it takes to run the dose, every four hours until the baby is born. Then you’re unhooked and free to move around.” She says she’s even put IVs in clients who preferred to labour in a tub.

What if you give birth before you can get antibiotics?

You’ll be kept in the hospital for 48 hours for observation. Symptoms to watch for in your baby include fever, difficulty feeding, a blueish tinge to the skin, irritability and lethargy. But know that GBS is uncommon after a baby reaches one month old and extremely rare after three months. “The effects of GBS are very preventable,” says Ladhani. “That’s why we focus on it so much.”

Read more:
What prenatal testing can tell you
Why your baby’s gut bacteria is so important
Why you should delay baby’s first bath

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