The cost-effectiveness of testing for Group B Streptococcus in pregnancy based on a cluster randomised trial (GBS3)

Group B Streptococcus (GBS) is a bacterium present in the vagina and lower gut of approximately one in four pregnant women. GBS can come and go throughout pregnancy and is usually symptomless, but may be passed to the baby around birth. Approximately one baby in every 1750 will develop a GBS infection within seven days of birth. Most will recover, but each year in the UK about 40 babies die and one in 14 of the survivors will have a long-term disability.

The objective of this study is to assess the cost-effectiveness of routine testing of women for GBS colonisation either in late pregnancy or during labour, compared to the current risk factor based strategy.

The economic evaluation, which takes the form of an economic modelling study, is being conducted as part of a multi-centre prospective two-group parallel cluster randomised controlled superiority trial with internal pilot (GBS3). Up to 320,000 women will be recruited from 80 maternity units (obstetric unit or alongside maternity unit) in England, Scotland and Wales.

A decision-analytic model will be constructed that will allow us to extrapolate the cost-effectiveness of alternative testing strategies for GBS colonisation and the usual risk factor approach in pregnancy beyond the parameters of the GBS3 trial.