Influenza vaccination during pregnancy: A systematic review of fetal death, spontaneous abortion, and congenital malformation safety outcomes

Results do not indicate that maternal influenza vaccination is associated with an increased risk of fetal death, spontaneous abortion, or congenital malformations. Statistical imprecision and clinical and methodological heterogeneity of the observational studies mean it is not possible to totally exclude adverse effects. Further studies investigating women vaccinated during their first trimester should be the highest priority to allow for more precise estimates, especially for spontaneous abortion, and congenital abnormality outcomes.