Study find surprising link between miscarriages and flu vaccines

A new study finds a surprising link between miscarriages and flu vaccines.
By Joseph Scalise | Sep 14, 2017
An analysis of U.S. pregnancies found that women who had back-to-back annual flu shots that included protection against swine flu between 2010 and 2012 were more likely to have miscarriages than those who did not receive the injections.

This new information is quite surprising. In fact, it has puzzled so many researchers that the Centers for Disease Control and Prevention have reached out to the American Congress of Obstetricians and Gynecologists in order to help them prepare for any expectant mothers that might become worried at the news.

"I want the CDC and researchers to continue to investigate this," said Dr. Laura Riley, a Boston-based obstetrician who was not involved in the research, according to ABC News. "But as an advocate for pregnant women, what I hope doesn't happen is that people panic and stop getting vaccinated."

Previous studies have shown that flu vaccines are safe during pregnancy. However, there has been little research on how much the shots affect the body when they are given in the first three months.

The study sought to fix that by focusing solely on miscarriages, which occur inuy the first 19 weeks of pregnancy. Researchers discovered that women who received a just one shot that included protection against swine flu were typically free of any complications. Most of the miscarriages came from women who had also received a shot the previous season.

Though the study was thorough, the first group did contain more women who are naturally at a high risk for miscarriage, such as older moms and smokers. Even so, the team believes they did a good job of balancing out such differences to get accurate data.

In addition, while the new information could help researchers better understand the way vaccines affect pregnancy, there were some complications to the study. Not only do some experts believe that the flu vaccine is not strong enough to trigger an immune system response that could cause a miscarriage, but there is also a chance some of the miscarriages were the result of swine flu. As a result, researchers still believe pregnant women should receive vaccinations until more information is known.

"Additional studies are needed to address the concern raised by this study," said Haywood Brown, president of The American of Congress of Obstetricians and Gynecologists who was not involved in the research, according to The Washington Post. "In evaluating all of the available scientific information, there is insufficient information to support changing the current recommendation, which is to offer and encourage routine flu vaccinations during pregnancy regardless of the trimester of pregnancy."

To expand on the findings, the team is currently working on a larger study that will look at recent data to find any other links between vaccines and miscarriages. They hope such information will be ready sometime next year.

The new findings are published in the journal Vaccine.

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