(HealthDay News) – Women receiving trivalent influenza vaccination are less likely to experience a stillbirth, especially for births occurring just after influenza season, according to a study published in Clinical Infectious Diseases.

Annette K. Regan, MPH, from the University of Western Australia in Crawley, and colleagues examined the incidence of stillbirth following seasonal trivalent influenza vaccination in a cohort of 58 008 births occurring between April 2012 and December 2013.

The researchers found that 8.8% of pregnant women received trivalent influenza vaccination and there were 377 stillbirths. Among unvaccinated and vaccinated women, there were 5.0 and 3.0 stillbirths per 100 000 pregnancy-days, respectively. Stillbirth was 51% less likely among vaccinated mothers compared with unvaccinated mothers after adjustment for confounders (adjusted hazard ratio [HR]: 0.49). Births occurring just after influenza season had the largest relative reduction in stillbirths (adjusted HR: 0.33).

“Mothers who received seasonal trivalent influenza vaccination during pregnancy were significantly less likely to experience stillbirth compared with unvaccinated mothers,” the authors write. “These results support the safety of seasonal influenza immunization during pregnancy and suggest a protective effect.”

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  1. Regan AK, Moore HC, de Klerk N, et al. Seasonal Trivalent Influenza Vaccination During Pregnancy and the Incidence of Stillbirth: Population-Based Retrospective Cohort Study. Clin Infect Dis. 2016; doi:10.1093/cid/ciw082.