It is time to address an issue that has comes up quite regularly. It is the question of ‘transience’ and confusion surrounding that particular word. We hear from mums as well as their health professionals some version of the following statement: “the reason we don’t test for group B Strep is because it is transient, meaning one day you can have it and the next day you don’t.”
This is simply not true. Group B Strep is not like the #27 bus, as we like to say here in the office. So let’s first take a look at several medical definitions of the word, transient.
- lasting only for a short time; impermanent
- passing away in time: existing temporarily
- short-lived; passing; not permanent; said of a disease or an attack.
- pertaining to a condition that is temporary or of short duration, usually not
It becomes a bit tricky when people are using the word while ill-informed about group B Strep in general and health professionals and lay-people are using the word synonymously with the description ‘comes and goes.’ Something that is defined as usually not recurring cannot also mean that it is here today gone tomorrow then back again.
GBS can come and go from the vagina quite naturally over a period of time. The result of a sensitive test for GBS carriage (ECM or PCR) is highly predictive for the next 5 weeks. So a test at 35-37 weeks of pregnancy is very good at predicting whether you will be carrying when you are most likely to go into labour – during the following 5 weeks(1). This 35-37 week window is considered optimal for testing for GBS carriage and is period during which the many countries which offer antenatal screening for GBS do so.
Tests taken later than 37 weeks will still give you an accurate indication as to your carriage status; however, there is a chance that your results will not be available when you go into labour. It would be a shame to do the test then not get the results until after your baby is born!
If the test is taken earlier than 35 weeks, then the chance that your carriage status has changed upon delivery increases (i.e. that you have either picked up GBS carriage, or that you have lost it). UK guidelines recommend that, if you have had any positive GBS test result (from the vagina, rectum or urine) during your current pregnancy, you should be offered intravenous antibiotics from the onset of labour or membrane rupture until delivery.
As far as GBS carriage over longer periods of time is concerned, at the present there isn’t good solid data that can predict carriage beyond a year. A woman who tests positive for group B carriage in her first pregnancy might not be a carrier in her second or third and vice versa. However, there is an increased chance of a woman carrying GBS in a pregnancy if GBS has been detected previously(2,3,4,5), so it is the view of our medical panel that, if possible, the pregnant woman should be offered a sensitive (ECM or PCR) test at 35-37 weeks of pregnancy to establish whether she is still carrying GBS.
The bottom line, as far as we’re concerned, is that even if this natural bacterium continues to be (incorrectly) considered ‘transient’ by some health professionals, that does not make it irrelevant! Isn’t prevention better than cure? We believe that every woman should be fully informed about group B Strep and offered the opportunity to have a sensitive (ECM) test to detect GBS carriage late in pregnancy.
The results of these tests can then be used to inform as to what further action may be needed, if any, to minimise the risk of GBS infection in the newborn baby. For more information on testing, please follow this link: http://gbss.org.uk/what-is-gbs/testing-for-gbs/ecm-test-where-how/
1. Yancey MK, Schuchat A, Brown LK, Ventura VL, Markenson GR. The accuracy of late antenatal screening cultures in predicting genital group B streptococcal colonization at delivery. Obstet Gynecol. 1996 Nov;88(5):811-5.
2. Cheng PJ, Chueh HY, Liu CM, Hsu JJ, Hsieh TT, Soong YK. Risk factors for recurrence of group B streptococcus colonization in a subsequent pregnancy. Obstet Gynecol. 2008 Mar;111(3):704-9.
3. Page-Ramsey SM, Johnstone SK, Kim D, Ramsey PS. Prevalence of Group B Streptococcus Colonization in Subsequent Pregnancies of Group B Streptococcus-Colonized versus Noncolonized Women. Am J Perinatol. 2012 Sep 21.
4. Turrentine MA, Ramirez MM. Recurrence of group B streptococci colonization in subsequent pregnancy. Obstet Gynecol. 2008 Aug;112(2 Pt 1):259-64
5. Colicchia LC, Lauderdale DS, Du H, Adams M, Hirsch E. Recurrence of group B streptococcus colonization in successive pregnancies. J Perinatol. 2015 Mar;35(3):173-6