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Group B Streptococcus

Extracted from Myles Textbook for Midwives 15th Edition. Diane M. Fraser, Margaret A. Cooper (Eds). London; Churchill Livingstone: 2009. Courtesy Elsevier.

Group B streptococcus (GBS) is the leading cause of serious neonatal infection in the UK, and affects between 0.5/1000 and 1.15/1000 live births.

GBS is a gram positive bacterium that naturally colonises the genital and gastrointestinal tracts, and is carried asymptomatically by up to 40% of adults. It is not considered to be a sexually transmitted disease but infection increases with sexual activity and rates are highest among women attending genitourinary medicine clinics.

In pregnant women colonised with GBS, there is a high risk of vertical transmission in pre-term delivery, prolonged rupture of membranes, or maternal pyrexia during labour. GBS is able to infiltrate the amniotic cavity, whether or not the membranes are intact, and infect the fetus. Postpartum endometritis and post-caesarean wound infection may also occur in the mother.

In the USA, pregnant women are screened in the third trimester and treated prophylactically if identified as high risk of transmitting the infection. However, routine screening in the UK is not considered clinically- or cost-effective.

The Practising Midwife featured articles 


Group B streptococcus infection  TPM 2013;16(7):27 - 30. Authors: Jane Plumb, Ginny Clayton 

Who safeguards mothers? TPM 2014;17(10):26 - 28. Author: Sara Wickham 

Further reading 

Royal College of Obstetricians & Gynaecologists (2012). The prevention of early-onset neonatal group B streptococcal disease. Green-top guideline No 36.


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