Universal antenatal screening for group B streptococcus may cause more harm than good

Dear Editor,

Seedat et al in their paper “Universal antenatal screening for group B streptococcus may cause more harm than good”(1) rehearse the reasons given by the UK National Screening Committee (NSC) for not recommending universal antenatal testing for group B Streptococcus, based on a NSC-commissioned review. Although they acknowledge that in the USA, authorities such as the Centre for Disease Control and Prevention (https://www.cdc.gov/groupbstrep/about/), the American College of Obstetricians and Gynecologists, and the American Academy of Pediatrics have concluded after rigorous review that testing and intrapartum antibiotic prophylaxis (IAP) should be recommended because it cause more good than harm (a conclusion echoed by the European Consensus Conference in 2014 (2) and the World Health Organisation in 2015 (3)), the title of Seedat et al’s paper (missing a question mark to indicate uncertainty) is unfortunately being interpreted by some as indicating that there is clear evidence that it causes more harm than good.

The UK’s risk-based prevention strategy has been in place since 2003. Unlike countries that have implemented GBS testing strategies, the UK rate of early-onset group B Strep infection has not fallen but increased and is now almost 20% higher than before the risk-based strategy was introduced - and more than two and a half times the rate in the USA where testing and IAP are universally recommended. Seedat et al fail to highlight not only the failure of the UK risk based approach to reduce early onset GBS infection rates, but that fact that it results in many women receiving IAP when they are not even GBS carriers. Daniels et al (4) reported that in the UK 21% of women carried group B Strep and 22% of women had risk factors for early onset neonatal GBS disease. However, the women are not in the same groups: of the women with risk factors and thus eligible for intrapartum antibiotic prophylaxis (IAP), 71% did not carry group B Strep, and of the women who carried group B Strep, 70% had no risk factors.

Group B Strep Support acknowledge that it would be ideal to avoid giving IAP to women whose babies will not develop early onset GBS disease and we would welcome research to establish which strains of GBS are pathogenic and which babies are susceptible, so that the use of IAP could be restricted to those at highest risk. We would also welcome a safe, effective and affordable group B Strep vaccine. Neither approach is currently available. Until it is, testing will prevent more group B Strep infections, disabilities and deaths than the current risk-based approach.

Seedat et al raise the concern that IAP will cause alterations to the microbiome but fail to highlight that most studies showing persistent alterations in the microbiome relate to caesarean section, and the use of broad-spectrum antibiotics prior to this procedure. GBS IAP should be predominantly with narrow spectrum penicillin, and the effects are accordingly less marked and have not been shown to persist after the first three months of life (5). Nor have long term effects been noted; for example Metz et al6 comment “We did not find a significant association between intrapartum GBS antibiotic prophylaxis and early childhood BMI Z-scores when compared to healthy controls (GBS negative with no antibiotic exposure). These findings may provide reassurance to clinicians who are concerned about the effect of fetal exposure to antibiotics for GBS prophylaxis”. Seedat et al suggest that “Maternal anaphylaxis is another important harm to consider, as it has potentially fatal consequences” but report one case of anaphylaxis resulting from GBS prophylaxis in the UK over three years – approximately one case per two million births.

We need more knowledge and better tools to combat early onset GBS disease. Until we have them, testing is the best cost-effective solution available, and we consider that the choice of whether to have testing for GBS is most appropriately made by women and their families rather than by the National Screening Committee.

Reference List

(1) Seedat F, Geppert J, Stinton C, Patterson J, Freeman K, Johnson SA et al. Universal antenatal screening for group B streptococcus may cause more harm than good. BMJ 2019; 364:l463.
(2) Di Renzo GC, Melin P, Berardi A, Blennow M, Carbonell-Estrany X, Donzelli GP et al. Intrapartum GBS screening and antibiotic prophylaxis: a European consensus conference. J Matern Fetal Neonatal Med 2015; 28(7):766-782.
(3) World Health Organisation. WHO recommendation on intrapartum antibiotic administration to women with group B Streptococcus (GBS) colonization for prevention of early neonatal GBS infection. https://extranet.who.int/rhl/topics/preconception-pregnancy-childbirth-a... . accessed 22-3-2019.
(4) Daniels JP, Gray J, Pattison HM, Gray R, Hills RK, Khan KS. Intrapartum tests for group B streptococcus: accuracy and acceptability of screening. BJOG 2011; 118(2):257-265.
(5) Stearns JC, Simioni J, Gunn E, McDonald H, Holloway AC, Thabane L et al. Intrapartum antibiotics for GBS prophylaxis alter colonization patterns in the early infant gut microbiome of low risk infants. Sci Rep 2017; 7(1):16527.
(6) Metz TD, McKinney J, Allshouse AA, Knierim SD, Carey JC, Heyborne KD. Exposure to group B Streptococcal antibiotic prophylaxis and early childhood body mass index in a vaginal birth cohort. J Matern Fetal Neonatal Med 2019;1-6.