What are the risks of GBS (group B streptococcus) infection during pregnancy?

 Most pregnant women who carry GBS bacteria have healthy babies. However, there’s a small risk that GBS can pass to the baby during childbirth. Rarely, GBS infection in newborn babies can cause serious complications that can be life-threatening.

Extremely rarely, GBS infection during pregnancy can also cause miscarriage, early (premature) labour or stillbirth.

What is GBS?

GBS is one of many bacteria that can be present in our bodies. It usually causes no harm. This situation is called carrying GBS or being colonised with GBS.

GBS is commonly found in the digestive system and the female reproductive system. It’s estimated that about one in four pregnant women in the UK carry GBS.

Around the time of labour and birth, many babies come into contact with GBS and are colonised by the bacteria. Most babies are unaffected, but a small number can become infected.

Early-onset GBS infection

If a baby develops GBS infection less than seven days after birth, it’s known as early-onset GBS infection. Most babies who become infected develop symptoms within 12 hours of birth.

It’s estimated that about one in 2,000 babies born in the UK and Ireland develops early-onset GBS infection. This means that every year in the UK (with 680,000 births a year) around 340 babies will develop early-onset GBS infection.

What complications can it cause?

Most babies who become infected can be treated successfully and will make a full recovery.

However, even with the best medical care, one in 10 babies diagnosed with early-onset GBS infection will die. The infection can cause life-threatening complications, such as:

  • blood poisoning (septicaemia),
  • infection of the lung (pneumonia), or
  • infection of the lining of the brain (meningitis).

Another one-in-five babies who survive the infection will be affected permanently. Early-onset GBS infection can cause problems such as cerebral palsy, deafness, blindness and serious learning difficulties.

Rarely, GBS can cause infection in the mother. For example, an infection in the womb or urinary tract, or more seriously, an infection that spreads through the blood, causing symptoms to develop throughout the whole body (sepsis).

Preventing early-onset GBS infection

The Royal College of Obstetricians and Gynaecologists (RCOG) has published guidance for healthcare professionals on preventing early-onset GBS infection. For more information, see Is my baby at risk of early-onset GBS infection?

Late-onset GBS infection

Late-onset GBS infection develops seven or more days after a baby is born. This is not usually associated with pregnancy. The baby probably became infected after the birth. For example, they may have caught the infection in hospital from someone else.

GBS infections after three months of age are extremely rare.


NHS Choices

Published Date 2010-07-23

Last Review Date 2009-09-13

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