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Effect of Influenza Vaccination in the First Trimester of Pregnancy

Sheffield, Jeanne S. MD; Greer, Laura G. MD; Rogers, Vanessa L. MD; Roberts, Scott W. MD; Lytle, Heather MD, MSPH; McIntire, Donald D. PhD; Wendel, George D. Jr MD

doi: 10.1097/AOG.0b013e318263a278
Original Research

OBJECTIVE: To estimate the effect of first-trimester influenza vaccination on fetal and neonatal outcomes.

METHODS: This was a retrospective cohort study examining delivery and neonatal outcomes after antepartum exposure to the seasonal trivalent inactive influenza vaccine. Data were collected and entered into an established computerized database. Outcomes by trimester of vaccination were then compared with women who did not receive the vaccine.

RESULTS: During the 5-year study period, 10,225 women received the seasonal influenza vaccine antepartum; 8,690 of these delivered at our institution, 439 in the first trimester and 8,251 in the second and third trimesters. Women vaccinated antepartum were significantly older with higher parity than women who declined vaccination. Neonates born to mothers receiving the vaccine in any trimester did not have an increase in major malformations regardless of trimester of vaccination (2% regardless of vaccination group, P=.9). Stillbirth (0.3% compared with 0.6%, P=.006), neonatal death (0.2% compared with 0.4%, P=.01), and premature delivery (5% compared with 6%, P=.004) were significantly decreased in the vaccinated group.

CONCLUSION: Influenza vaccination in the first trimester was not associated with an increase in major malformation rates and was associated with a decrease in the overall stillbirth rate. This information will aid in counseling women regarding the safety of influenza vaccination in the first trimester.


Influenza vaccination in the first trimester of pregnancy does not increase major fetal malformations but does result in a decrease in stillbirth.

From The University of Texas Southwestern Medical Center and Parkland Health & Hospital System, Dallas, Texas.

Corresponding author: Jeanne S. Sheffield, MD, 5323 Harry Hines Boulevard, Dallas, TX 75390-9032; e-mail:

Financial Disclosure The authors did not report any potential conflicts of interest.

© 2012 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.