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What is the swab test at 37 weeks pregnant


Group B Strep and Pregnancy (for Parents)

What Is Group B Strep?

Group B Streptococcus (group B strep, GBS) is a type of

bacteriaoften found in the urinary tract, digestive system, and reproductive tracts. The bacteria come and go from our bodies, so most people who have it don't know that they do. GBS usually doesn't cause health problems.

What Problems Can Group B Strep Cause?

Health problems from GBS are not common. But it can cause illness in some people, such as the elderly and those with some medical conditions. GBS can cause infections in such areas of the body as the blood, lungs, skin, or bones.

About 1 out of every 4 women have GBS. In pregnant women, GBS can cause infection of the urinary tract, placenta, womb, and amniotic fluid.

Even if they haven't had any symptoms of infection, pregnant women can pass the infection to their babies during labor and delivery.

How Does Group B Strep Affect Babies?

When women with GBS are treated with antibiotics during labor, most of their babies do not have any problems. But some babies can become very sick from GBS. Premature babies are more likely to be infected with GBS than full-term babies because their bodies and immune systems are less developed.

The two types of GBS disease in babies are:

  1. Early-onset infections, which happen during the first week of life. Babies often have symptoms within 24 hours of birth.
  2. Late-onset infections, which develop weeks to months after birth. This type of GBS disease is not well understood.

What Are the Signs & Symptoms of GBS Disease?

Newborns and infants with GBS disease might show these signs:

  • a fever
  • feeding problems
  • breathing problems
  • irritability or fussiness
  • inactivity or limpness
  • trouble keeping a healthy body temperature

Babies with GBS disease can develop serious problems, such as:

  • pneumonia
  • sepsis
  • meningitis (infection of the fluid and lining around the brain). Meningitis is more common with late-onset GBS disease and, in some cases, can lead to hearing loss, vision loss, learning disabilities, seizures, and even death.

How Is Group B Strep Diagnosed?

Pregnant women are routinely tested for GBS late in the pregnancy, usually between weeks 35 and 37. The test is simple, inexpensive, and painless. Called a culture, it involves using a large cotton swab to collect samples from the vagina and rectum. These samples are tested in a lab to check for GBS. The results are usually available in 1 to 3 days.

If a test finds GBS, the woman is said to be "GBS-positive." This means only that she has the bacteria in her body — not that she or her baby will become sick from it.

GBS infection in babies is diagnosed by testing a sample of blood or spinal fluid. But not all babies born to GBS-positive mothers need testing. Most healthy babies are simply watched to see if they have signs of infection.

How Is Group B Strep Treated?

Doctors will test a pregnant woman to see if she has GBS. If she does, she will get intravenous (IV) antibiotics during labor to kill the bacteria. Doctors usually use penicillin, but can give other medicines if a woman is allergic to it.

It's best for a woman to get antibiotics for at least 4 hours before delivery. This simple step greatly helps to prevent the spread of GBS to the baby.

Doctors also might give antibiotics during labor to a pregnant woman if she:

  • goes into labor prematurely, before being tested for GBS
  • hasn't been tested for GBS and her water breaks 18 or more hours before delivery
  • hasn't been tested for GBS and has a fever during labor
  • had a GBS bladder infection during the pregnancy
  • had a baby before with GBS disease

Giving antibiotics during labor helps to prevent early-onset GBS disease only. The cause of late-onset disease isn't known, so no method has yet been found to prevent it. Researchers are working to develop a vaccine to prevent GBS infection.

Babies who get GBS disease are treated with antibiotics. These are started as soon as possible to help prevent problems. These babies also may need other treatments, like breathing help and IV fluids.

How Can I Help Prevent Group B Strep Infection?

Because GBS comes and goes from the body, a woman should be tested for it during each pregnancy. Women who are GBS-positive and get antibiotics at the right time during labor do well, and most don't pass the infection to their babies.

If you are GBS-positive and begin to go into labor, go to the hospital rather than laboring at home. By getting IV antibiotics for at least 4 hours before delivery, you can help protect your baby against early-onset GBS disease.

Reviewed by: Thinh Phu Nguyen, MD

Date reviewed: July 2022

Group B strep test | Pregnancy Birth and Baby

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If you’re pregnant, one of the routine antenatal tests you’ll probably have is for group B streptococcus (also known as ‘group B strep’ or ‘GBS’). This page explains what the test is for, which babies are at risk of infection and how group B strep is treated.

What is group B strep?

Group B strep is a type of bacteria commonly found in the intestines, rectum, urethra or vagina. Many women have it, and it usually causes no health concerns or symptoms. Some women infected with group B strep get a urinary tract infection, and it increases the risk of a miscarriage only very slightly.

The main concern is passing it on to the baby before or during a vaginal birth. While many babies who get infected stay healthy, a small proportion (about 1 in 200) become very sick within the first few days of life. They get serious infections such as pneumonia and blood poisoning, or meningitis, which is an infection around the brain.

These seriously ill babies are treated with intravenous antibiotics. Most recover with no side-effects, but some don't survive.

Group B strep test

The group B strep test is a routine antenatal test. It involves taking a swab of the inside of the vagina. Your doctor or midwife will do this, or you may be able to do it yourself. The swab is taken at 35 to 37 weeks' pregnancy. Tests done earlier in your pregnancy aren't a good guide to your condition at birth because the bacteria can come and go.

Who has the group B strep test?

Some hospital and doctors recommend that every pregnant woman has a group B strep test.

But others ask only some women to have the test if they are at higher-than-average risk because they go into labour early, or their waters break early.

Even if you're planning a caesarean, you can think about having the test in case your waters break early or you go into labour unexpectedly early.

Talk about the risks and benefits of the group B strep test with your midwife or doctor.

Risk factors for infection with group B strep

Babies are more likely to be infected with group B strep if:

  • they are born, or your waters break, before 37 weeks
  • you give birth more than 18 hours after your waters break
  • you have a fever (over 38°C) while in labour
  • you've had a previous child with severe group B strep infection
  • a urine test during pregnancy detected group B strep
  • a swab taken no more than 5 weeks earlier detected group B strep

Preventing group B strep from infecting your baby

If your group B test at 35 to 37 weeks was positive, or if you have the risk factors listed above, your doctor or midwife will probably recommend that you have intravenous antibiotics when your waters break or labour starts.

Often this is penicillin, but alternatives are available if you are allergic to penicillin. The antibiotics pass through the placenta and into the baby. This greatly reduces your baby's chances of becoming ill.

There's no need for antibiotics before a planned caesarean because the baby will not pass through the vagina. You can't pass the bacteria to your baby through the placenta.

After the birth

If you had antibiotics during labour, your baby will be monitored for the first couple of days for signs of infection. The chance of your baby being infected is low.

Late-onset group B strep

There is a very small group of babies that develop group B strep infection weeks or months after birth (called ‘late onset group B strep'). They become seriously ill quite quickly, with fevers and vomiting and difficulty feeding. Unfortunately, the group B strep test and use of antibiotics doesn’t prevent a baby developing late-onset group B strep infection.

If your child's condition deteriorates quickly, call triple zero (000) and ask for an ambulance, or go to the nearest hospital emergency department.

When to seek help

If you want more information about group B strep, or if you have any concerns about your baby, call Pregnancy, Birth and Baby on 1800 882 436 to speak to a maternal child health nurse, or talk to your midwife or doctor.

Sources:
RANZCOG (Group B Streptococcus), RANZCOG (Maternal Group B Streptococcus in pregnancy), Cochrane Database of Systematic Reviews (Vaginal chlorhexidine during labour to prevent early-onset neonatal group B streptococcal infection), Cochrane Database of Systematic Reviews (Intrapartum antibiotics for known maternal Group B streptococcal colonization), Department of Health (Pregnancy Care Guidelines, Group B streptococcus)

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: May 2020


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