Abstract

BACKGROUND: Pregnant women were identified as a population of priority for vaccination during the H1N1 influenza pandemic outbreak in 2009. OBJECTIVES: To assess adverse fetal outcomes following the administration of H1N1 pandemic vaccination during pregnancy. SEARCH STRATEGY: PubMed, Embase, and Cochrane Library were searched up to January 2017. SELECTION CRITERIA: Cohort studies investigating fetal outcomes after H1N1 influenza vaccination during pregnancy were eligible. The language was limited to English. DATA COLLECTION AND ANALYSIS: Pairs of reviewers independently screened studies for eligibility, assessed the risk of bias, and extracted data from the included studies. MAIN RESULTS: A total of 19 cohort studies were eligible. The use of vaccines during any period of pregnancy was associated with lower risk of stillbirth (adjusted hazard ratio 0.80, 95% confidence interval 0.69-0.92). No significant differences were found between the vaccinated versus unvaccinated groups in terms of the risks of spontaneous abortion, premature birth, and small for gestational age. CONCLUSIONS: The administration of H1N1 vaccines during pregnancy might reduce the risk of stillbirth, a complication associated with H1N1 infection. The quality of evidence was, however, not adequate to reach a definitive conclusion.
Pregnant women Safety Influenza