Hi Kelli,
So many parents are blind-sided when they have tested negative for group B strep.
Here are two studies on how often colonization status can change between screening and delivery:
Virranniemi M, Raudaskoski T, Haapsamo M, et al. The effect of screening-to-labor interval on the sensitivity of late-pregnancy culture in the prediction of group B streptococcus colonization at labor: A prospective multicenter cohort study. Acta Obstet Gynecol Scand. 2019; 98: 494-499. https://doi.org/10.1111/aogs.13522
"Between late-pregnancy screening and labor, GBS colonization changed from negative to positive in 3.2% and from positive to negative in 2.5% of the women.” (Note: this study was done in Finland)
Stephens K, Charnock-Jones D, Smith G
Group B Streptococcus and the risk of perinatal morbidity and mortality following term labor
American Journal of Obstetrics & Gynecology, 2023; 228, S1305-S1312
The authors note that 6% of GBS carriers at the time of delivery will remain undetected despite the culture being performed within 5 weeks of birth.
The older US CDC guidelines from 2010 (current guidelines are at acog.org/gbs <http://acog.org/gbs>) stated:
"Although maternal GBS colonization might increase clinical suspicion for early-onset GBS disease in an infant, in the era of universal screening, >60% of early-onset GBS cases have occurred among infants born to women who had a negative prenatal GBS culture screen (102,203,204). False-negative cases are not unexpected because culture at 35–37 weeks’ gestation will fail to detect some women with intrapartum GBS colonization. As effective prevention strategies are increasingly implemented, a growing proportion of the remaining relatively low burden of disease will reflect inherent limitations in the strategies. Signs of sepsis in any newborn can be an indication of early-onset GBS disease, regardless of maternal colonization status.” (Note the last sentence!!)
102. Van Dyke MK, Phares CR, Lynfield R, et al. Evaluation of universal antenatal screening for group B Streptococcus. N Engl J Med 2009;360:2626–36. 203. Pulver LS, Hopfenbeck MM, Young PC, Stoddard GJ, Korgenski K, Daly J, et al. Continued early onset group B streptococcal infections in the era of intrapartum prophylaxis. J Perinatol 2009;29:20–5. 204. Puopolo KM, Madoff LC, Eichenwald EC. Early-onset group B streptococcal disease in the era of maternal screening. Pediatrics 2005;115:1240–6. "
Perhaps those with clinical backgrounds or industry partners would like to comment on what should be understood about the limitations of current screening. Certainly, proper specimen collection is important. More on that topic soon!
Marti
CHIFA profile: Marti Perhach is CEO/Cofounder of Group B Strep International, United States. Professional interests: Group B strep disease research and prevention, prenatal infection, One Health. Email address: marti.perhach AT gbs-intl.org