Universal maternal testing for group B streptococcus in late pregnancy: process outcomes and alongside qualitative study for the GBS3 trial

Abstract

Background: One in five pregnant women/birthing people carry group B streptococcus in the gut or genital tract, and over half of them will pass it to their child during pregnancy, labour (most commonly) or after birth. Most babies exposed to maternal GBS remain well, but 1 in 1750 newborns in the UK and Ireland develop early-onset GBS infection. Introducing routine testing for group B streptococcus (GBS) for all pregnant women and birthing people in late pregnancy may reduce cases of early-onset infection in the newborn but would likely increase the number of women given antibiotics during labour. The GBS3 trial (ISRCTN49639731) is a cluster-randomised trial involving approximately 320,000 women/birthing people from 80 maternity units in England and Wales. It will determine the clinical and cost-effectiveness of routine testing, compared to the current risk-factor based strategy.

Methods: To obtain details of the timing, coverage and outcome of the testing process and use of IAP, about 130 consecutive maternity records of women who birthed after 32 weeks' gestation and who were not scheduled for a planned caesarean birth, and the corresponding neonatal records, were scrutinised at each participating maternity unit. We performed a baseline qualitative study to inform the trial design to explore women's views on the acceptability of different methods of GBS testing in pregnancy, including self-swabbing procedures. We explored the acceptability of different methods of routine testing for GBS colonisation to pregnant women and health care professionals (HCPs), and examined the barriers and facilitators to their implementation.

Results: We received detailed demographic data for 9179 women. Overall, in both testing groups, 72 % of women were offered a vaginal-rectal swab for GBS. Of those women offered a swab, 82 % accepted a vaginal-rectal swab. Of the women with a swab taken, 17 % were positive for GBS. 87 % of women had a test result ≥ 4 hours before birth. Our baseline and embedded qualitative studies found that GBS testing is acceptable to most women and HCPs.

Conclusion: GBS testing is acceptable to pregnant women and health care professionals in the UK. When GBS testing is offered to eligible women, the offer is accepted, the test performed and a result available to guide the offer of IAP in a timely fashion for the majority of women.

Keywords: Enriched culture medium testing; Group B streptococcus; Intrapartum antibiotic prophylaxis; Pregnancy; Rapid testing; Screening; Testing.