Group B Streptococcus (GBS)


The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

What is group B Streptococcus during pregnancy?

Also known as Streptococcus agalactiae, group B Streptococcus (GBS) is a group of bacteria that can infect anybody and do so in various parts of the body. GBS is a particular problem in pregnancy as it can enter through the cervix as an ascending infection – an infection that moves upward through the birth canal. The name Streptococcus means that the bacteria are spherical cells (cocci) and form chains (strepta) by attaching end-to-end like the cars in a train. GBS often inhabits the vagina and rectum in healthy women. When it ascends, however, GBS can cause diseases, such as endometritis (inflammation of the lining of the uterus), chorioamnionitis (inflammation of the fetal membranes and amniotic fluid), and urinary tract infections (UTI). (Various other types of bacteria also can cause these three conditions.) Most of the time, GBS does not hurt you. However, if you do harbor GBS and you are pregnant, the GBS has the potential to harm the baby, regardless of whether or not you suffer from endometritis, chorioamnionitis, or UTI. For this reason, pregnant women are screened routinely for GBS. 

How common is GBS infection during pregnancy?

GBS are normal inhabitants of the vagina and rectum in about 25 percent or more (some studies report rates up to 40 percent) of healthy women. Factors increasing the risk that you carry GBS include diabetes, cancer, infection with HIV, liver disease; in other words, conditions that interfere with your immune system. Despite a high proportion of pregnant women carrying GBS, actual neonatal GBS infection, only strikes 1 to 2 infants for every 1,000 births.

Situations that can cause GBS to ascend through the birth canal increasing the risk to the baby, include repeated digital examinations by the doctor (fingers inserted into the vagina or rectum), your water breaking early (premature rupture of membranes [PROM], preterm premature rupture of membranes [PPROM, and prolonged rupture of membranes), and a long period of time (more than 18 hours) between rupture of the membranes and delivery. Other factors increasing the chance that your baby will suffer a GBS infection include the development of chorioamnionitis, a UTI, or other infections, you develop a fever, you previously had a baby with GBS disease, or the baby is born prematurely (prior to 37 weeks).

How is GBS infection during pregnancy diagnosed?

Because GBS is present in so many women, all pregnant women are screened for GBS as a component of routine prenatal care. A few weeks before delivery, generally at 36-37 weeks gestation, your obstetrician will swab samples from your vagina and rectum. Samples will be cultured in a laboratory to see if GBS is present. If you do have GBS, the laboratory will analyze your samples further to determine to which antibiotics your particular GBS strains are most susceptible.

Does GBS cause problems during pregnancy?

GBS can cause maternal infections that can make the mother ill, such as endometritis, chorioamnionitis, and UTI, but the major concern with GBS is that it can cause neonatal infection.

Does GBS cause problems for the baby?

GBS is a common source of neonatal sepsis (infection throughout the blood and tissues of the newborn), neonatal meningitis (infection of the connective tissue layers surrounding the brain), and neonatal pneumonia. GBS can also cause spontaneous abortion (miscarriage), or stillbirth, plus, if GBS gives you a UTI, chorioamnionitis, or endometritis, this can lead to preterm labor and preterm birth, which further increases risk of meningitis, pneumonia, and other neonatal health problems. Affected infants may not suck milk or formula adequately and will lose a substantial amount of weight after birth, and will not gain weight as quickly as a healthy neonate. They also may be fussy or irritable, with a fairly low amount of muscular activity (they wont move so much).

What to consider about taking medications when you are pregnant or breastfeeding:

  • The risks to yourself and your baby if you do not treat the GBS infection
  • The risks and benefits of each medication you use when you are pregnant
  • The risks and benefits of each medication you use when you are breastfeeding

What should I know about using medication to treat GBS during pregnancy?

If your screening test shows that you carry GBS, you will be given an antibiotic medication intravenously (IV) during labor to prevent neonatal GBS infection. The antibiotic of choice is penicillin unless you have a penicillin allergy. If you have penicillin allergy but are not at high risk of suffering an anaphylactic reaction, your doctor may give you cefazolin. Otherwise, the next two options are clindamycin and erythromycin, but your GBS cultures must be tested to see if they are susceptible to either of these antibiotics. If you carry GBS that is resistant both to clindamycin and erythromycin, in many cases, the next choice will be vancomycin.

Who should NOT stop taking medication for GBS during pregnancy?

Regimens of antibiotic medication must be taken through their full course to ensure that the infection is eliminated.

What should I know about choosing a medication for my GBS during pregnancy?

It is important to stay in communication with your health care provider as the release of new studies over time can change the outlook on the role of specific medications during pregnancy.

You may find Pregistrys expert reports about the medications to treat this condition here. Additional information can also be found in the sources listed below.

What should I know about taking a medication for my GBS when I am breastfeeding?

Penicillin, clindamycin, and vancomycin are generally considered fairly safe during pregnancy.

What alternative therapies besides medications can I use to treat my GBS infection during pregnancy?

There are no alternatives to antibiotic medication.

What can I do for myself and my baby when I have a GBS infection during pregnancy?

It is very important to follow the instructions of your physician.

Resources for GBS in pregnancy:

For more information about GBS during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or contact the following organizations:

Read the whole report
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.

Read articles about Group B Streptococcus (GBS)