Flu Shot Does Not Cause Pregnant Women to Miscarry

A new study conducted by investigators at the Center for Clinical Epidemiology and Population Health at the Marshfield Clinic Research Institute in Wisconsin has found the influenza (flu) vaccine does not cause miscarriages in pregnant women. These results were discovered after the Centers for Disease Control and Prevention tasked the researchers with investigating the results of a smaller study conducted during the 2010-11 and 2011- 12 flu seasons that found an increased risk for spontaneous abortion, or miscarriage, in the 28 days after a pregnant woman is vaccinated, but only in a small number of women who received the H1N1 vaccine two years in a row. There was no association between miscarriage and vaccination among women who had not been vaccinated in the previous year.

The new study, which examined the 2012-13, 2013-14 and 2014-15 flu seasons individually and together, matched 1,236 pairs of women, including 627 pairs who had been vaccinated in the previous season and 609 pairs who were not. For each flu season and even when all women and seasons were combined, there was no evidence of increased miscarriage risk after the flu vaccine during the first 28 days. In addition, there was no significant association between miscarriage and the flu vaccine in the 29- to 56-day risk window and beyond. “It didn’t seem to matter which season of flu or whether they were vaccinated in the prior season or not,” said lead investigator James Donahue, a senior epidemiologist at Marshfield. “The findings provide a high level of reassurance regarding the safety of influenza vaccine in early pregnancy and through pregnancy, and support the current recommendations of an influenza vaccination for all pregnant women.”