Effect of Maternal Influenza Vaccination on Spontaneous Abortion and Stillbirth: A systematic review and meta-analysis Open Access

Bratton, Kristin Nicole (2014)

Permanent URL: https://etd.library.emory.edu/concern/etds/bc386j68h?locale=en


Influenza vaccination is recommended in pregnancy and has been demonstrated to have beneficial effects on the health of both the mother and infant. Although the effects of antenatal influenza vaccination on other adverse birth outcomes have been characterized, this is the first systematic review meta-analysis of the association between influenza vaccination during pregnancy and stillbirth and spontaneous abortion. We identified and analyzed studies that assessed outcomes of stillbirth or spontaneous abortion after administration of influenza vaccine during pregnancy. A literature search was conducted using the electronic databases Medline, EMBASE, Web of Science, Cumulative Index to Nursing or Allied Health Literature, Scopus, Google Scholar, and the Cochrane Central Register of Controlled Trials. 21 studies met inclusion criteria for the descriptive literature review. Seven of these 21 studies were selected for a quantitative meta-analysis, which was restricted to studies that defined stillbirth as fetal loss prior to 20 or 22 weeks and/or spontaneous abortion as fetal loss after 20 or 22 weeks. Data were extracted from articles using apre-tested tool and a risk of bias assessment was performed for each study. Pooled estimates for the effects of seasonal influenza vaccine, pH1N1 vaccine, and vaccination overall were calculated for each outcome. The pooled relative risk estimate showed a protective effect of influenza vaccination in pregnancy against stillbirth (RR: 0.65, (0.46, 0.84)), and the effect remained significant when the analysis was restricted to the pH1N1 vaccine (RR: 0.68 (0.54, 0.86)). The pooled effect for spontaneous abortion was not significant (RR: 0.97, (0.46, 1.48)). There was no heterogeneity of effect estimates detected for either outcome (I2=0%). These analyses add to the evidence base for safety of influenza vaccination in pregnancy. The finding of a protective effect of maternal influenza vaccination on stillbirth warrants inclusion of this outcome in future observational and interventional studies.

Table of Contents

Background and Literature Review...p1 Introduction...p7 Methods...p8 Results...p11 Discussion...p15 Public Health Implications...p19



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