Estimating the impact of parvovirus B19 outbreaks on congenital anomalies and fetal outcomes in Wales.
OBJECTIVES: Parvovirus B19 (B19V) is a common infection that can cause complications in pregnancy. Outbreaks of B19V in Europe and the UK were recorded in 2024. We aimed to describe the epidemiology of maternal parvovirus in Wales and to investigate associated fetal outcomes widely and in 2024 specifically. STUDY DESIGN: A retrospective observational study. METHODS: All cases of maternal B19V reported to the Congenital Anomaly Register Information Service (CARIS) were analysed. Maternal risk factors included gestational age at the time of infection and maternal age. Spatio-temporal analysis was performed to look for clusters. Poisson regression was used to model incidence of maternal B19V over time. Fetal outcomes were tested for association with risk factors using linear regression and Fisher's exact test. Outcomes and congenital anomalies were descriptively analysed. RESULTS: Between 1998 and 2025, there were 79 cases of maternal B19V across 81 fetuses, mostly reported in South Wales (74/81, 91.3%). There were 24 (29.6%) cases of at least one confirmed congenital anomaly and 57 (70.3%) cases reporting no anomalies; 53 (93%) of these cases had a positive outcome. Congenital anomalies were associated with worse fetal outcomes. Excluding terminations, the overall fetal survival rate was 88%. No association between maternal risk factors and fetal outcome was identified. There was an increase in cases in 2024 with an increase in fetal losses. CONCLUSIONS: The 2024 European B19V outbreak led to an increase in maternal cases and negative fetal outcomes in Wales.