Group B Streptococcus (GBS) is a type of bacteria commonly found in the gastrointestinal tract or the back of your throat, known as strep throat.
Group B strep (GBS) is also found in the vagina and rectum, and colonizes around 10-30% of women during pregnancy. The bacteria can be passed onto your baby just before or during birth.
Many babies who become infected aren’t affected. But about 1 in 200 babies get serious infections such as blood poisoning (sepsis), pneumonia, and meningitis.
Depending on where you live, routine screening for GBS during pregnancy might or might not be recommended by your health care provider.
Read on for more information about the group B strep test, how it is done, and your choices about having this test.
Group B strep test
Recommendations for routine GBS screening are currently a matter of debate among global health experts.
The evidence varies in terms of how best to identify mothers who need antibiotic treatment, and the potential negative side effects of antibiotics during pregnancy.
Leading health experts in the US and Australia recommend pregnant women between 35 and 37 weeks be routinely screened for group B strep (GBS) if they have ruptured waters for 72 hours or more.
In Europe, some countries recommend routine screening, yet others take a risk-based management view. There are also countries that don’t have national guidelines at all.
In the UK, routine screening for group B strep isn’t recommended.
What is group B strep?
GBS (group b streptococcus) is a bacterial group commonly found in the intestinal, vaginal, and rectal areas. In healthy adults, group B strep poses few problems
People might be walking around in the community with group B strep, and have no signs and symptoms of it.
Group B streptococcal infection can, however, cause a serious illness known as group B strep disease, which is dangerous for adults with chronic health conditions, and for your unborn baby.
Group B strep pregnancy
If you are colonized by GBS bacteria, it doesn’t necessarily mean you will pass the bacteria on to your baby, but it does increase the risk.
There are two main types of group B strep disease in babies:
- Early-onset disease. Group B strep symptoms begin within a week of birth, but almost all newborns will have symptoms within 24-48 hours.
- Late-onset disease. Group B strep infection occurs in newborns within a week, or within the first month.
Group B strep infection is caused by the direct transfer of bacteria from mother to baby at the time of birth.
Group B strep test procedure
The group B streptococcal test is done by high and low vaginal cotton swabs and a urine test in pregnancy.
The midwife will ask you to lie on the exam table, on your back with ankles together and knees flopped out.
The midwife will insert a speculum (in the same way as when you have a cervical screen) and do the first swab (HVS), then take out the speculum to do the second swab at the bottom of your vagina and rectum (LVS).
If your waters have broken, this might be confirmed when the speculum exam is done.
You will then be asked to provide a urine sample.
Does group B strep test hurt?
The actual test is a swab; it might be uncomfortable, but it shouldn’t be painful at all.
Your doctor or midwife might do the group B streptococcus swab, or you might be shown how to do it for yourself. This could be an option if you have any concerns or anxiety about being swabbed.
Group B strep tests interpretation
The group B strep test is called a culture. The sample is collected and then tested in a lab to see if any of the group B strep bacteria have grown. The results are usually available between 1 and 3 days.
If the lab test finds group B strep in the sample, the results will come back as positive.
This means the woman has the bacteria in her body; it does not necessarily mean she or her baby will become sick from it.
Group B strep UTI treatment
Infection with GBS can cause urinary tract infection (UTI) in pregnancy and is found in your urine.
Urinary tract infections in pregnancy can irritate the cervix, causing early contractions. It’s best to get a urine test if you are concerned, and then follow up the test results with your health care provider.
Urinary tract infections caused by GBS infection are usually treated with antibiotics, such as penicillin and ampicillin.
Group B strep test UK
Leading health authorities in the UK, including those at the National Institute of Health and Social Care Excellence (NICE) and the National Screening Committee, don’t recommend routine GBS screening in pregnancy.
These health experts have reviewed the available research and have determined there’s not enough clear evidence to demonstrate that routine screening would be beneficial.
NICE is also concerned about the cost-effectiveness of routine screening.
The key reasons for not offering routine GBS testing are:
- Most babies born to mothers who are GBS positive don’t become infected
- It’s unclear whether screening during pregnancy does more harm than good, as treating many mothers and babies would potentially prevent only a very small number of infections
- Research has shown treatment with antibiotics during labor doesn’t have any effect on baby deaths from infection.
- There are serious concerns about using antibiotics on this scale. Ongoing research has shown the negative effects of antibiotics on healthy bacteria in mothers and babies. Antibiotic resistance is a concern if given to newborns from birth; it can affect them over their lifetime
- There is an increased risk of interventions during labor, resulting in poor outcomes for mother and baby, including an increased risk of a c section.
- Routine screening programs are carried out at 35-37 weeks gestation; this means mothers of preterm babies haven’t been screened.
UK mothers will be offered antibiotics specifically for GBS infection if they have:
- A fever
- Prolonged rupture of membranes (longer than 18 hours before delivery)
- Tested positive to the group B strep test during pregnancy
- Previously had a baby with group B strep
- Gone into preterm labor.
Pregnant women who wish to be screened and have the group B strep test, or who have risk factors for group B strep, can discuss it with their health care provider and find out how to arrange a test.
Group B strep test positive
You will be offered antibiotics by your doctor if your group B strep results are positive.
Depending on how close you are to having your baby, your health care provider might request another group B strep test after 37 weeks, and advise antibiotics, administered into a vein, during labor.
The decision to commence antibiotic treatment must not be taken lightly. Research the risks versus benefits to yourself and your baby.
Discuss it with a trusted health care professional. The group B strep can be transitional, meaning it can come and go.
Group B Strep During Pregnancy – What You Need To Know has more information.
Can you test negative for group B strep and still have it?
If your test comes back negative, that should mean you can relax, enjoy your pregnancy and prepare for the arrival of your baby.
However, it’s not uncommon for care providers to want to take another test when labor begins. This is called a rapid test, and is usually done if your care provider suspects you are at risk of GBS infection.
The problem is that GBS can develop at any time. Research shows that many women have different test results for group B strep infection between a routine third-trimester screening and a rapid test performed at the time of labor.
Who should have a group B strep test?
It’s recommended any pregnant woman with a history of recurrent group B streptococcus infection should undergo testing.
You should especially consider this if:
- Your waters break and you don’t go into labor within a certain time frame
- You go into premature labor
- You have other health problems and your doctor recommends the test and antibiotics during labor.
Can I decline the group B test?
The group B strep test in pregnancy is recommended but it’s not routine for everyone. Even if you fall into the risk categories, it’s up to you to decide whether to have the test or decline it.
Be as informed as possible about the risks, as opposed to the benefits, of having the test, and make the decision that’s best for you and your baby.
Talk to your health care provider about informed consent if you want to decline any test in pregnancy or labor.