Ohfuji S, Deguchi M, Tachibana D, et al. - Researchers conducted this prospective cohort study of 10,330 pregnant women in order to determine the safety of influenza vaccination in terms of adverse birth outcomes. Questionnaires before and after the 2013/2014 influenza season were used to determine influenza vaccination during pregnancy. Six hundred forty-one (10%) among 6,387 unvaccinated pregnant women and 356 (9%) among 3,943 vaccinated pregnant women reported to exhibit adverse birth outcomes. The analysis suggests no increase in the risk of adverse birth outcomes in correlation with influenza vaccination during pregnancy; this was observed regardless of the trimester in which vaccination was performed, compared with unvaccinated pregnant women.