Giving pregnant women the flu shot is expected not only to prevent the flu in both mothers and newborns, but also to prevent adverse pregnancy outcomes such as preterm birth. According to Hutcheon, however, this cannot actually be proved because sample sizes would have to be too large.
QUOTE: “This suggests that the large fetal benefits from influenza vaccination observed in epidemiologic studies are unlikely to be causal.”
Phadke et al (2016), in a comment on this study, writes “studies in which investigators have accounted for influenza circulation have demonstrated a consistent protective effect against a variety of adverse birth outcomes; those studies include the only randomized controlled trial designed a priori and adequately powered to do so.”
Hutcheon replies that their results “specifically apply to the limited time window of possible benefit ..”
NOTE: The take-home message here is that although flu shots are already being recommended, the benefits they claim may or may not be true, as the scientists involved in the research don’t all agree. If you choose to obtain a flu shot during pregnancy, please get it at your doctor’s office rather than at the convenient pharmacy or supermarket (where the shots still contain mercury). And be sure to specify that you want the kind without mercury.