A cross-sectional study of immune seroconversion to SARS-CoV-2 in front-line maternity health professionals

COVID-19, the respiratory disease caused by the SARS-CoV-2, is thought to cause a milder illness in pregnancy with a greater proportion of asymptomatic carriers. This has important implications for the risk of patient-to-staff, staff-to-staff and staff-to patient transmission among health professionals in maternity. The aim of this study was to investigate the prevalence of previously undiagnosed SARS-CoV-2 infection in health professionals from two tertiary-level maternity units in London, UK and to determine associations between HCW characteristics, reported symptoms and serological evidence of prior SARS-CoV-2 infection.

200 anaesthetists, midwives and obstetricians with no previously confirmed diagnosis of COVID-19 were tested for immune seroconversion using laboratory IgG assays. Comprehensive symptom and medical histories were also collected. 5/40 (12.5%; 95% CI: 4.2-26.8) anaesthetists, 7/52 (13.5%; 95% CI: 5.6-25.8%) obstetricians and 17/108 (15.7%; 95% CI: 9.5-24.0%) midwives were seropositive, with an overall total of 29/200 (14.5%; 95% CI: 9.9-20.1%) of maternity healthcare workers testing positive for IgG antibodies against SARS-CoV-2. Of those who had seroconverted, 10/29 (35.5%) were completely asymptomatic. Fever or cough were only present in 6/29 (20.7%) and (10/29 (34.5%) respectively. Anosmia was the most common symptom occurring in 15/29 (51.7%) seropositive participants and was the only symptom that was predictive of positive seroconversion (OR 18; 95% CI 6 – 55). 58.6% of those who were seropositive had not self-isolated at any point and continued to provide patient care in the hospital setting.

This study was the largest study of baseline immune seroconversion in maternity healthcare workers conducted to date and reveals that 1 in 6 were seropositive, of whom 1 in 3 were asymptomatic. This has significant implications for the risk of occupational transmission of SARS-CoV-2 for both staff and patients in maternity and regular testing of staff, including asymptomatic staff should be considered to reduce transmission risk.