What is the benefit of screening for B streptococcus bacteria during pregnancy?

Photo of a pregnant woman with her daughter
PantherMedia / Leo Lintang

Pregnant women who have a greater risk of infecting their baby with group B streptococcus are given an antibiotic during labor. This is done to protect the baby from . It’s not clear whether it makes sense to routinely screen for group B streptococcus in all pregnant women.

Routine tests are carried out during pregnancy to see whether the baby is developing normally and the mother is healthy. These tests include ultrasound scans and blood tests, as well as urine tests. In Germany, special guidelines (“Mutterschafts-Richtlinien”) specify what is to be tested in pregnancy, and what sorts of tests are used.

If doctors think that a pregnant woman carries group B streptococcus in her body, she is given an antibiotic during labor. This is done to prevent the baby from being infected and becoming very ill.

Group B streptococcus bacteria: Harmless for adults, but dangerous for babies

Group B streptococcus may live in the human body, especially in the bowel and genital area.

In healthy adults, group B streptococcus usually don't cause any problems. That’s different in newborn babies: Then the bacteria can lead to blood poisoning (septicemia) or even death. Group B streptococcus can also cause various infectious diseases in babies, such as meningitis or pneumonia, and result in permanent disability.

About 1,800 out of 10,000 pregnant women in Germany carry group B streptococcus in their body. The can be spread to the baby during a natural (vaginal) birth. In Germany, about 3 out of 10,000 newborns develop a group B streptococcus . Only very rarely do they die of it.

Group B streptococcus test in pregnancy

The group B streptococcus test can be done to find out whether a pregnant woman has these in her body. The test is typically offered towards the end of pregnancy, between 34 and 36 completed weeks of pregnancy.

In Germany, the costs of this test are covered by all statutory health insurers if the doctor or midwife thinks that the pregnant woman has group B streptococcus in her body or if there's a risk of premature birth. If a woman would like to have the test done even though the doctor doesn't think she has these in her body, she has to pay for it herself. Then the test is offered as an individual health care service (in German: individuelle Gesundheitsleistung, or IGeL for short). Some statutory health insurers cover the costs of the test for all pregnant women, though.

The test usually involves taking two smear samples: one from the vagina and one from the anal area. These cell samples are typically sent to a laboratory and the results are usually available within a week. If the test finds group B streptococcus in the woman's cells, it is recorded in her maternity-related medical records (in German: Mutterpass).

When is the baby at greater risk of infection?

It’s assumed that the baby's risk of is higher if the pregnant woman has at least one of the following risk factors:

  • Group B streptococcus are found in a urine sample.
  • Group B streptococcus are found in the vaginal or anal area (group B streptococcus test).
  • There is a risk of premature birth before 38 completed weeks of pregnancy.
  • The woman develops fever during birth, i.e. a body temperature of 38°C or higher.
  • At least 18 hours pass between the mother's water breaking and the birth.
  • The woman has already given birth to another child that became infected with group B streptococcus during the birth.

If the baby has a higher risk of , then the woman is given an antibiotic during the birth to protect the child from . This antibiotic is either injected or given as an infusion (IV drip).

Group B streptococcus bacteria screening during pregnancy

In some countries, all women are routinely screened for group B streptococcus towards the end of their pregnancy. This routine test is known as group B streptococcus . The current guidelines issued by the German Society of Gynecology and Obstetrics also recommends this type of .

If the test shows of group B streptococcus in the sample taken from a pregnant woman, she is usually given an antibiotic during birth. If the test doesn't find any streptococcus , no antibiotic is needed. There are two exceptions in which an antibiotic will still be given even if the test doesn’t detect any group B streptococcus :

  • The woman has already given birth to another child that became infected with group B streptococcus during the birth.
  • Group B streptococcus were found in the pregnant woman’s urine.

Research on screening for group B streptococcus bacteria

The Institute for Quality and Efficiency in Health Care (IQWiG, Germany) looked into the advantages or disadvantages of routinely for group B streptococcus in all pregnant women. The researchers at IQWiG wanted to compare group B streptococcus with the approach of giving an antibiotic during birth if the woman has specific risk factors.

But they didn't find any good-quality studies on the advantages or disadvantages of the test for mothers and their babies. So it remains unclear whether babies can be better protected from a group B streptococcus by a test or by the approach based on risk factors. It is also not clear whether the test helps women to avoid taking although they don’t need to.

Gemeinsamer Bundesausschuss (G-BA). Richtlinien des Gemeinsamen Bundesausschusses über die ärztliche Betreuung während der Schwangerschaft und nach der Entbindung („Mutterschafts-Richtlinien“). April 21, 2016.

Gesellschaft für Neonatologie und pädiatrische Intensivmedizin (GNPI). Prophylaxe der Neugeborenensepsis - frühe Form - durch Streptokokken der Gruppe B (S2k-Leitlinie). AWMF-Registernr.: 024-020. March 2016.

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Screening for serological group B streptococci within the framework of the medical check-ups according to the maternity Guidelines: Final report; Commission S17-02. December 11, 2018. (IQWiG Reports; Volume 688).

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Created on August 29, 2019
Next planned update: 2022


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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