Study prompts call to examine flu vaccine and miscarriage

September 13, 2017 by Mike Stobbe
In this Aug. 27, 2010 file photo, a nurse practitioner prepares a flu vaccination in Rockville, Md. A puzzling study of U.S. pregnancies suggests that women who received back-to-back flu shots between 2010 and 2012—after a new swine flu vaccine came out—more often had miscarriages. (AP Photo/Evan Vucci, File)

A puzzling study of U.S. pregnancies found that women who had miscarriages between 2010 and 2012 were more likely to have had back-to-back annual flu shots that included protection against swine flu.

Vaccine experts think the results may reflect the older age and other miscarriage risks for the , and not the flu shots. Health officials say there is no reason to change the government recommendation that all be vaccinated against the flu. They say the flu itself is a much greater danger to women and their fetuses.

The Centers for Disease Control and Prevention has reached out to a doctor's group, the American Congress of Obstetricians and Gynecologists, to warn them the study is coming out and help them prepare for a potential wave of worry from expectant moms, CDC officials said.

"I want the CDC and researchers to continue to investigate this," said Dr. Laura Riley, a Boston-based obstetrician who leads a committee on maternal immunization. "But as an advocate for pregnant women, what I hope doesn't happen is that people panic and stop getting vaccinated."

Past studies have found flu vaccines are safe during pregnancy, though there's been little research on impact of flu vaccinations given in the first three months of pregnancy.

Flu and its complications kill thousands of Americans every year. The elderly, young children and pregnant women are especially at risk. When a new "swine flu" strain emerged in 2009, it killed 56 U.S. pregnant women that year, according to the CDC.

The study's authors, two of whom are CDC researchers, saw a big difference when they looked at women who had miscarried within 28 days of getting a shot that included protection against swine flu, but it was only when the women also had had a the previous season.

They found 17 of 485 miscarriages they studied involved women whose vaccinations followed that pattern. Just four of a comparable 485 healthy pregnancies involved women who were vaccinated that way.

The first group also had more women who were at higher risk for miscarriage, like older moms and smokers and those with diabetes. The researchers tried to make statistical adjustments to level out some of those differences but some researchers don't think they completely succeeded.

Other experts said they don't believe a shot made from killed could trigger an immune system response severe enough to prompt a miscarriage. And the authors said they couldn't rule out the possibility that exposure to swine flu itself was a factor in some miscarriages.

Two other medical journals rejected the article before a third, Vaccine, accepted it. Dr. Gregory Poland, Vaccine's editor-in-chief, said it was a well-designed study that raised a question that shouldn't be ignored. But he doesn't believe flu shots caused the miscarriages. "Not at all," said Poland, who also is director of research at the Mayo Clinic.

Though this study may cause worry and confusion, it is evidence "of just how rigorous and principled our vaccine safety monitoring system is," said Jason Schwartz, a Yale University vaccine policy expert.

Some of the same researchers are working on a larger study looking at more recent data to see if a possible link between vaccine and miscarriage holds up, said James Donahue, a study author from the Minnesota-based Marshfield Clinic Research Institute. The results aren't expected until next year at the earliest, he said.

Explore further: Study charts flu shot's impact on pregnant women and their babies

Related Stories

Study charts flu shot's impact on pregnant women and their babies

August 1, 2017
Pregnant women and young babies are among those most at risk for complications, hospitalization, and death from the flu. While doctors have long recommended flu shots for protection, experts weren't exactly sure how the shots ...

All pregnant women need flu shot: Ob/Gyn group

August 19, 2014
(HealthDay)—A group representing U.S. obstetricians is calling for all pregnant women to get a flu shot.

More pregnant women getting flu shot, but improvement needed

December 8, 2016
(HealthDay)— Getting a flu shot during pregnancy can protect both a mom-to-be and her baby. And while the percentage of pregnant American women who got the vaccine has doubled in recent years, too many still go without ...

Effectiveness of influenza vaccine for pregnant women may differ by trimester

February 1, 2016
In a study to be presented on Feb. 5 in an oral concurrent session at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Atlanta, researchers will present findings from a study titled, T-follicular ...

Swine flu jab harmless to unborn babies

September 21, 2016
The swine flu vaccine, when administered to pregnant women, caused neither fetal injury nor infant death, writes Karolinska Institutet professor Johan F Ludvigsson an opinion piece in Tuesday's Dagens Nyheter in conjunction ...

Recommended for you

Americans are getting more sleep

January 19, 2018
Although more than one in three Americans still don't get enough sleep, a new analysis shows first signs of success in the fight for more shut eye. According to data from 181,335 respondents aged 15 and older who participated ...

Wine is good for you—to a point

January 18, 2018
The Mediterranean diet has become synonymous with healthy eating, but there's one thing in it that stands out: It's cool to drink wine.

Sleep better, lose weight?

January 17, 2018
(HealthDay)—Sleeplessness could cost you when it's time to stand on your bathroom scale, a new British study suggests.

Who uses phone apps to track sleep habits? Mostly the healthy and wealthy in US

January 16, 2018
The profile of most Americans who use popular mobile phone apps that track sleep habits is that they are relatively affluent, claim to eat well, and say they are in good health, even if some of them tend to smoke.

Improvements in mortality rates are slowed by rise in obesity in the United States

January 15, 2018
With countless medical advances and efforts to curb smoking, one might expect that life expectancy in the United States would improve. Yet according to recent studies, there's been a reduction in the rate of improvement in ...

Can muesli help against arthritis?

January 15, 2018
It is well known that healthy eating increases a general sense of wellbeing. Researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have now discovered that a fibre-rich diet can have a positive influence ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.