GBS in last pregnancy

hi all I had group b strep with my son and thankfully found out really early so there were no surprises, im currently expecting my third baby 17+5 weeks, I have been tested for it with this pregnancy aswell and I was told I was clear, however I have also been told that GBS can come and go and is not always there to be detected and can come back, well this has me worried about labour, I spoke to my midwife and she said not to worry well this has not eased my worries in the slightest can anyone help

2 Replies

  • In my area if you've ever been tested strep b positive they automatically put you on antibiotics in labour. You haven't mentioned how far along you are but the test I think should be done around 35 weeks. I would persist with your midwife and let her know you'd like the antibiotics.

  • Hi Hspread,

    Firstly, many congratulations!

    As you may already know, carrying GBS has no symptoms - the only way to find out if you’re carrying GBS is to be tested.

    Testing for GBS not routine on the NHS & the usual NHS vaginal swab test gives lots of false negative results. The NHS test is reliable for positive results but up to 50% of women carrying GBS when tested will be told they're not.

    GBS carriage can come & go so a positive result for GBS is not very predictive from one pregnancy to another, though it is very predictive for at least 5 weeks (and probably longer for an NHS test).

    A sensitive test for GBS carriage is available privately and from a few NHS hospitals - the ECM (or Enriched Culture Medium) test - around £35 for a postal service. Instructions are included & you pay when you send the swabs in to be cultured.

    Your or your health professional takes swabs from the low vagina and rectum and post them to the laboratory. If done within 5 weeks of delivery, this test is very sensitive: research showed a positive ECM result for GBS gave an 87% chance of still carrying GBS at delivery. Similarly, a negative result gave a 96% chance of still not carrying GBS at delivery.

    As Mandraki says, the best time to test is after 35 weeks of pregnancy. Earlier testing is not as good at predicting GBS colonisation at delivery, and testing after 37 weeks increases the chance that the baby will be born before the result is available.

    A small but growing number of NHS Trusts offer ECM testing and a postal service is available from a number of private laboratories. The test pack, processing the swabs and sending you the results will cost approximately £35. For the latest on testing for GBS, visit

    I do hope that helps, you may also find our page for pregnant women at useful. If you've got any other questions please do let us know.

    Best wishes,


You may also like...