Group B Streptococcus (GBS) Polymerase Chain Reaction (PCR) Concordance Study

The investigators are comparing three different methods of testing for an infection which is commonly found in women. The infection is caused by a bacterium called Group B Streptococcus. About 10-30% of women carry GBS in the vagina or rectum.

During labour this infection can be passed to the neonate. This can lead to the baby developing a serious infection.

However, research has shown that if antibiotic treatment is given to GBS carrying women during labour most of these infections can be avoided.

A new bedside test known as PCR has been shown to produce a GBS diagnostic result in less than an hour. In clinical trials conducted in the US and France this method has been shown to be more accurate than either prenatal vaginal swabs or risk factor assessment. For this reason, PCR may be helpful in screening and treating GBS positive women in the UK.

In this study the investigators will compare each of the following three methods of diagnosis to a gold standard.

• Prenatal vaginal culture swab (at 35 to 37 weeks gestation)- The US approach.
• Risk factor assessment (at the time of admission for labour)- The UK approach
• The new PCR test (at the time of your labour admission)

The investigators will compare the accuracy of each of these methods with the most accurate method for determining the GBS status during labour. This 'most accurate' method is a highly sensitive swab test which unfortunately takes several days to produce a result. For this reason this test will not tell the investigators whether prophylactic antibiotics may be useful during labour (Receiving them after birth is ineffective).

If PCR is shown to be a more accurate method of identifying GBS positive women this may help to reduce the number of infections in new born infants and as a result may help to save lives.