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INTRODUCTION — Group B streptococcus (GBS) is a bacterium that can cause serious infections in pregnant people, newborn babies, and infants less than age three months. GBS is one of many types of streptococcal bacteria, sometimes called "strep."
This article discusses the risks of GBS during pregnancy and ways to prevent complications of GBS.
WHAT IS GROUP B STREP INFECTION? — GBS is commonly found in the lower part of the digestive system (colon) and the vagina.
●Approximately one in three to four pregnant people in the United States "carries" GBS in their digestive tract and/or in their vagina. Carrying GBS is not the same as having an infection. Carriers are not sick and do not need treatment during pregnancy. There is nothing you can do to avoid carrying GBS.
●Pregnant women who are carriers of GBS infrequently develop GBS infections. GBS can cause urinary tract infections (typically involving only the bladder), infection of the amniotic fluid (the "bag of water" surrounding the fetus), and infection of the uterus after delivery. GBS infections during pregnancy may lead to preterm labor or, if the baby is infected while in the uterus, stillbirth.
●Pregnant women who carry GBS can pass on the bacteria to their newborns, and some of those babies become infected with GBS. Newborns who are infected with GBS can develop pneumonia (lung infection), septicemia (blood infection), and/or meningitis (infection of the lining of the brain and spinal cord). When a newborn is infected within the first few hours or days of life, this is called "early-onset" GBS.
Newborn GBS infection and infection of the uterus after delivery can usually be prevented by giving an intravenous (IV) antibiotic during labor to anyone who is a GBS carrier at delivery. (See 'Group B strep prevention' below.)
GROUP B STREP RISK FACTORS — You are at risk of being a GBS carrier at delivery if:
●You have a vaginal and rectal swab culture during your current pregnancy showing GBS
●You have a urine culture during your current pregnancy showing GBS
●You had an infant infected with GBS in the past
If you did not have a vaginal and rectal swab culture performed, but your urine culture during your current pregnancy did not show GBS and you did not have an infant infected with GBS in the past, then you are considered at risk of being a GBS carrier at delivery only if:
●You go into labor prematurely (more than three weeks before your due date)
●You have a fever ≥100.4 degrees Fahrenheit during labor
●You have ruptured membranes ("broken water") for ≥18 hours before delivery
TESTING FOR GROUP B STREP — Tests are done during pregnancy to determine if a person is a carrier of GBS.
Urine culture — Most doctors and nurses recommend a urine culture early in your pregnancy to be sure that you do not have a bladder infection without symptoms. If your urine culture shows GBS or other bacteria, you may be treated with an oral antibiotic. If you have symptoms of urinary tract infection, such as burning pain with urination, any time during your pregnancy, a urine culture should be done. If GBS grows from the urine culture, this infection should be treated with an oral antibiotic, but you should also receive an IV antibiotic during labor. (See 'Group B strep prevention' below.)
Routine screening for GBS — Expert groups recommend that anyone who is pregnant have routine "culture" testing. This involves swabbing the vagina and rectum between 360/7ths weeks (36 weeks, 0 days) and 376/7th weeks (37 weeks, 6 days) of pregnancy. The sample is then tested in a laboratory. If your GBS culture is positive, you will be given an IV antibiotic during labor. (See 'Group B strep prevention' below.)
GROUP B STREP PREVENTION — If you are found to have GBS during pregnancy, even if you have no symptoms of infection, you will receive intravenous (IV) antibiotics during labor to significantly lower the risk of passing the bacteria on to your newborn.
Being treated with an antibiotic during labor greatly reduces the chance that you or your newborn will develop a serious infection related to GBS in the first week after delivery.
Penicillin is the antibiotic typically used in this situation, although another drug may be used if you have a penicillin allergy. (See 'If you have a penicillin allergy' below.)
If you go into preterm labor — If you go into preterm (premature) labor before you’ve been tested to find out if you carry GBS, a swab culture will be done when you are admitted to the hospital (see 'Routine screening for GBS' above). Then you will be treated with an IV antibiotic until your baby is born or the labor is stopped by your health care provider.
If you have a C-section — If you have a planned cesarean birth ("C-section"), you will not need IV antibiotics because the risk of passing GBS on to the newborn is much lower than with a vaginal delivery. However, even if you plan ahead to have a C-section, you should still be tested for GBS during pregnancy. This is because if the test is positive, you will need IV antibiotics if you go into labor before the scheduled C-section date.
If you have a penicillin allergy — If you have an allergy to penicillin, be sure your doctor (and all your health care providers) are aware of this allergy early in your pregnancy. Tell them exactly what type of reaction you have had in the past. If you had only a rash that was not hives, or only itching but no rash, this is not considered a serious allergy. On the other hand, trouble breathing, swelling of your face, and/or hives does suggest a serious, life-threatening allergy. Many people who have reason to think they are allergic to penicillin may not be truly allergic when they have formal allergy testing done by a physician. Obstetricians now recommend that pregnant people with a history of penicillin allergy have skin testing to confirm the allergy. This can be done safely during pregnancy.
If you have a nonserious penicillin allergy, you can receive a common drug related to penicillin. If you have a serious allergy and you carry GBS, your GBS should be tested in the laboratory to determine which antibiotic should be used during labor.
Late-onset GBS — It is important to note that young infants up to age three months can also develop sepsis, meningitis, and other serious infections from GBS. Being treated with an antibiotic during labor does not reduce the chance that your baby will develop this later type of infection that begins after the first week of life. There is currently no way to prevent this late-onset GBS disease.
WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
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Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Prevention of early-onset group B streptococcal disease in neonates
Group B streptococcal infection in neonates and young infants
Group B streptococcal infection in pregnant individuals
Group B streptococcal infections in nonpregnant adults
Group B Streptococcus: Virulence factors and pathogenic mechanisms
Vaccines for the prevention of group B streptococcal disease
The following organizations also provide reliable health information.
●National Library of Medicine
●The Center for Disease Control and Prevention (available in Spanish)