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When is group b strep test in pregnancy
Group B strep test | Pregnancy Birth and Baby
Group B strep test | Pregnancy Birth and Baby beginning of content
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.
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)
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Last reviewed: May 2020
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Pregnancy checkups, screenings and scans
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Group B Streptococcus
Read more on RANZCOG - Royal Australian and New Zealand College of Obstetricians and Gynaecologists website
Pregnancy screening Group B Streptococcus (GBS) - Maternal, child and family health
The Pregnancy screening for Group B Streptococcus (GBS) consumer brochure provides information to all pregnant women on screening and recommended treatment for GBS.
Read more on NSW Health website
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Strep B Test: MedlinePlus Medical Test
What is a group B strep test?
Strep B, also known as group B strep (GBS), is a type of bacteria commonly found in the digestive tract, urinary tract, and genital area. It rarely causes symptoms or problems in adults but can be deadly to newborns.
In women, GBS is mostly found in the vagina and rectum. So a pregnant woman who is infected can pass the bacteria to her baby during labor and delivery. GBS can cause pneumonia, meningitis, and other serious illnesses in a baby. GBS infections are the leading cause of death and disability in newborns.
A group B strep test checks for GBS bacteria. If the test shows that a pregnant woman has GBS, she can take antibiotics during labor to protect her baby from infection.
Other names: group B streptococcus, group B beta-hemolytic streptococcus, streptococcus agalactiae, beta-hemolytic strep culture
What is it used for?
A group B strep test is most often used to look for GBS bacteria in pregnant women. Most pregnant women are tested as part of routine prenatal screening. It may also be used to test infants who show signs of infection.
Why do I need a group B strep test?
You may need a strep B test if you are pregnant. The American College of Obstetricians and Gynecologists recommends GBS testing for all pregnant women. Testing is usually done in the 36th or 37th week of pregnancy. If you go into labor earlier than 36 weeks, you may be tested at that time.
A baby may need a group B strep test if he or she has symptoms of infection. These include:
Trouble with feeding
Lack of energy (hard to wake up)
What happens during a group B strep test?
If you are pregnant, your health care provider may order a swab test or a urine test.
For a swab test, you will lie on your back on an exam table. Your health care provider will use a small cotton swab to take a sample of cells and fluids from your vagina and rectum.
For a urine test, you will most likely be told to use the "clean catch method" to ensure your sample is sterile. It includes the following steps.
Wash your hands.
Clean your genital area with a cleansing pad given to you by your provider. To clean, open your labia and wipe from front to back.
Start to urinate into the toilet.
Move the collection container under your urine stream.
Collect at least an ounce or two of urine into the container, which should have markings to indicate the amounts.
Finish urinating into the toilet.
Return the sample container as instructed by your health care provider.
If your baby needs testing, a provider may do a blood test or a spinal tap.
For a blood test, a health care professional will use a small needle to take a blood sample from your baby's heel. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. Your baby may feel a little sting when the needle goes in or out.
A spinal tap, also known as a lumbar puncture, is a test that collects and looks at spinal fluid, the clear liquid that surrounds the brain and spinal cord. During the procedure:
A nurse or other health care provider will hold your baby in a curled-up position.
A health care provider will clean your baby's back and inject an anesthetic into the skin, so your baby won't feel pain during the procedure. The provider may put a numbing cream on your baby's back before this injection.
The provider may also give your baby a sedative and/or pain reliever to help him or her better tolerate the procedure.
Once the area on the back is completely numb, your provider will insert a thin, hollow needle between two vertebrae in the lower spine. Vertebrae are the small backbones that make up the spine.
The provider will withdraw a small amount of cerebrospinal fluid for testing. This will take about five minutes.
Will I need to do anything to prepare for the test?
You don't any special preparations for group B strep tests.
Are there any risks to the test?
There is no risk to you from a swab or urine test. Your baby may have slight pain or bruising after a blood test, but that should go away quickly. Your baby will likely feel some pain after a spinal tap, but that shouldn't last too long. There is also a small risk of infection or bleeding after a spinal tap.
What do the results mean?
If you are pregnant and results show you have GBS bacteria, you will be given antibiotics intravenously (directly to your veins) during labor, at least four hours before delivery. This will prevent you from passing the bacteria to your baby. Taking antibiotics earlier in your pregnancy is not effective, because the bacteria can grow back very quickly. It's also more effective to take antibiotics through your vein, rather than by mouth.
You may not need antibiotics if you are having a planned delivery by Cesarean section (C-section). During a C-section, a baby is delivered through the mother's abdomen rather than vaginally. But you still should be tested during pregnancy because you may go into labor before your scheduled C-section.
If your baby's results show a GBS infection, he or she will be treated with antibiotics. If your provider suspects a GBS infection, he or she may treat your baby before test results are available. This is because GBS can cause serious illness or death.
If you have questions about your results or your baby's results, talk to your health care provider.
Learn more about laboratory tests, reference ranges, and understanding results.
Is there anything else I need to know about a group B strep test?
Strep B is one type of strep bacteria. Other forms of strep cause different types of infections. These include strep A, which causes strep throat, and streptococcus pneumoniae, which causes the most common type of pneumonia. Streptococcus pneumonia bacteria can also cause infections of the ear, sinuses, and bloodstream.
ACOG: The American College of Obstetricians and Gynecologists [Internet]. Washington D.C.: American College of Obstetricians and Gynecologists; c2019. Group B Strep and Pregnancy; 2019 Jul [cited 2019 Nov 15]; [about 3 screens]. Available from: https://www.acog.org/Patients/FAQs/Group-B-Strep-and-Pregnancy
Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Group B Strep (GBS): Prevention; [cited 2019 Nov 15]; [about 4 screens]. Available from: https://www.cdc.gov/groupbstrep/about/prevention.html
Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Group B Strep (GBS): Signs and Symptoms; [cited 2019 Nov 15]; [about 4 screens]. Available from: https://www.cdc.gov/groupbstrep/about/symptoms.html
Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Streptococcus Laboratory: Streptococcus pneumoniae; [cited 2019 Nov 15]; [about 3 screens]. Available from: https://www.cdc.gov/streplab/pneumococcus/index.html
Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Travelers' Health: Pneumococcal Disease; [updated 2014 Aug 5; cited 2019 Nov 15]; [about 3 screens]. Available from: https://wwwnc.cdc.gov/travel/diseases/pneumococcal-disease-streptococcus-pneumoniae
Intermountain Healthcare: Primary Children's Hospital [Internet]. Salt Lake City: Intermountain Healthcare; c2019. Lumbar Puncture in a Newborn; [cited 2019 Nov 15]; [about 4 screens]. Available from: https://intermountainhealthcare.org/ext/Dcmnt?ncid=520190573
Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2019. Blood Culture; [updated 2019 Sep 23; cited 2019 Nov 15]; [about 2 screens]. Available from: https://labtestsonline.org/tests/blood-culture
Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2019. Prenatal Group B Strep (GBS) Screening; [updated 2019 May 6; cited 2019 Nov 15]; [about 2 screens]. Available from: https://labtestsonline.org/tests/prenatal-group-b-strep-gbs-screening
Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2019. Urine Culture; [updated 2019 Sep 18; cited 2019 Nov 15]; [about 2 screens]. Available from: https://labtestsonline.org/tests/urine-culture
Michigan Medicine: University of Michigan [Internet]. Ann Arbor (MI): Regents of the University of Michigan; c1995–2021. Group B Streptococcal Infections in Newborns[cited 2021 Aug 6]; [about 3 screens]. Available from: https://www.uofmhealth.org/health-library/zp3014spec
University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2019. Health Encyclopedia: Group B Streptococcus Infection in Babies; [cited 2019 Nov 15]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=90&contentid=P02363
University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2019. Health Encyclopedia: Pneumonia; [cited 2019 Nov 15]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content. aspx?contenttypeid=85&contentid=P01321
WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy [Internet]. Geneva (SUI): World Health Organization; c2010. 6. Paediatric and neonatal blood sampling; [cited 2019 Nov 15]; [about 3 screens]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK138647
Test for group B streptococcus, Streptococcus agalactiae, culture with antibiogram
Group B streptococcus (GBS, GBS, Streptococcus agalactiae) is a Gram-positive bacterium (coccus) that in the human body can colonize the oropharynx, anal region of the rectum , vagina (usually vestibule), urogenital tract, skin. GBS is a commensal of the human gut microbiota. GBS causes severe illness in newborns - early neonatal infections such as sepsis, meningitis, pneumonia, osteomyelitis, arthritis and pyelonephritis, the frequency of which in different countries varies from 0.2 to 5 or more per 1000 live births and late neonatal infections . GBS also poses a risk to certain patients in other age groups. In obstetric practice, group B streptococcus is associated with bacteremia, urinary tract infections, chorioamnionitis, premature rupture of amniotic fluid, preterm labor, postpartum endometritis, etc.
Prevention of early morbidity in newborn GBS is possible: - In 89% of cases, if the first dose of antibiotic prophylaxis was given 2 hours before the birth of the child; - In 72% of cases, if the first dose of antibiotic prophylaxis was given less than 2 hours before the birth of the child, or there was a fever intranatally
2. If GBS is detected during differential diagnosis, prescribing antibiotics based on their sensitivity to the pathogen.
Composition of indicators:
Detection of group B streptococcus (Streptococcus agalactiae) with sensitivity to antibiotics
Method : Bacteriological, manual Measuring range : not applicable
0 - 120l
Fulfillment is possible on biomaterials:
9000 Delivery terms:
48 hours at 20 to 25 degrees Celsius
Amis Gel Vehicle (Female)
Patient Preparation Guidelines
Preparation Conditions (unless otherwise directed by physician): Within 24 hours Stop taking local antibacterial and antiseptic drugs. Immediately before the examination, do not toilet the external genital organs. Important: Be examined no earlier than 48 hours after a gynecological examination, vaginal ultrasound, colposcopy and other intravaginal gynecological procedures.
You can add this test to your shopping cart on this page
Prenatal screening at 35-37 weeks of gestation is done to identify pregnant women who are infected with Group B Streptococcus (GBS) to determine the need for IV antibiotic prophylaxis with onset labor, helps to prevent neonatal complications (sepsis, pneumonia and neonatal meningitis).
Group B streptococcus was not detected during prenatal screening at 35-37 weeks and there are no obstetric risk factors - there are no indications for antibiotic prophylaxis with the onset of labor.
Strept. Agalactiae (group B streptococci) (determination in the material by PCR)
Cost of analysis
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the price does not include the cost of taking biological material
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Analysis results ready
Regular*: 1-2 business days
Analysis submission date: Completion date:
*excluding the day of delivery.
Where and when you can take
Weekdays: from 7.45 to 21.00
Weekends: from 8.45 to 17.00
Changes in work schedule
Preparation for analysis
General recommendations for testing
For women: Tested after menstruation. Sexual life, douching, vaginal showers, the use of tampons, suppositories and other local preparations are prohibited for 24 hours. It is advisable not to take a bath. Only the external toilet of the genitals is allowed. It is advisable to take smears for infections and crops no earlier than 3 weeks after taking antibiotics (for any reason). This does not apply to the diagnosis of viral infections. For men: Do not urinate for 1.5-2 hours. It is advisable to take smears for infections and crops no earlier than 3 weeks after taking antibiotics (for any reason). This does not apply to the diagnosis of viral infections.
Methods and tests
PCR (polymerase chain reaction). Qualitative
Download a sample of the result of the analysis
What is it for
Group B streptococci (Streptococcus agalactiae) are bacteria found in the lower intestines of 10-35% of healthy men and in the vagina and/or lower intestines of 10-35% of healthy women. These bacteria are a normal part of the human microflora. Although group B streptococcus is generally safe for adults, it can cause serious complications during pregnancy and severe illness in newborns. Also, group B streptococcus can affect people with a weakened immune system, chronic diseases, and the elderly.
How can a newborn become infected with streptococcus
Most infections occur during childbirth. Possible infection with premature rupture of the membranes. It is possible that infection can also occur through intact fetal membranes.
Risk factors for streptococcal infection
presence of streptococcus on examination in vaginal discharge or urine;
rupture of membranes;
fever during labor;
mother's age less than 20 years;
streptococcal infection of the newborn in past births.
Streptococcal infection can threaten a newborn
First of all, infection with streptococcus is dangerous not for the mother, but for the baby.
Inflammation of the lungs (pneumonia)
Inflammation of the meninges - meningitis
Streptococci can cause septic complications
If infected before delivery, may cause premature birth, miscarriage, stillbirth.
What disorders can be caused by group B streptococcus in a pregnant woman and after childbirth
Usually streptococcus does not affect healthy adults, however, in rare cases, it can cause infectious complications in a pregnant woman:
Urinary tract infection
Infection of the placenta and amniotic fluid (chorioamnionitis)
Bacteremia (circulation of bacteria in the blood)
Terrible complication - sepsis
Rarely, after childbirth, streptococcus can cause inflammation and infection of the lining of the uterine cavity - endometritis
Streptococcus can cause wound infection in women after caesarean section
Should pregnant women be tested?
The first examination is desirable to be done in the first trimester of pregnancy, especially if there have been miscarriages or premature births in the past. It is advisable to re-examine at 35-37 weeks of pregnancy.
Testing is also recommended for elective caesarean section, even though the baby is not in contact with the birth canal.
How to test for streptococcus
Preliminary preparation for the delivery of the analysis is not required. An analysis for group B streptococcus is taken from the vagina with a special swab, which is placed in the environment and then analyzed in the laboratory by PCR.
What to do with the results of the analysis
If the test is negative, no action is required. If you test positive for group B streptococcus, it does not mean that you or your child will definitely get sick. But the risk of infection in this case is higher. To prevent diseases of the child during childbirth or in case of premature outflow of water, antibiotics are prescribed prophylactically.