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Move Over, Tylenol.
New research suggests that a common — but often overlooked — pregnancy complication may increase your chances of having a child with autism spectrum disorder (ASD).
The good news? If you treat it, the risk doesn’t seem to rise.
In the study, researchers looked at more than 51,000 women in Israel who gave birth between 2011 and 2017. Of them, 4,409 had abnormal thyroid hormone levels — some before pregnancy, some during and some both.
The team followed the women through January 2021 and found that thyroid dysfunction before and during pregnancy more than doubled the chances of their child having autism.
An estimated 1 in 31 children age 8 and older in the US has been diagnosed with ASD, a disorder affecting learning, behavior, communication and social interaction.
The researchers also discovered that the longer the thyroid problems lasted, the higher the likelihood of autism became. For example, children whose mothers had low thyroid hormone levels through all three trimesters faced more than three times the risk of being diagnosed with autism.
But there’s a silver lining: when thyroid problems were properly controlled during pregnancy, the risk didn’t rise significantly.
“We found that while adequately treated chronic thyroid dysfunction was not associated with increased autism risk in offspring, ongoing imbalance across multiple trimesters was,” Dr. Idan Menashe, a senior lecturer at Ben-Gurion University of the Negev and one of the study’s authors, said in a statement.
The thyroid is a small, butterfly-shaped gland at the front of your neck, just below the Adam’s apple. It produces hormones that regulate your metabolism, energy levels and other vital functions.
Those hormones are also critical for fetal brain development, especially early in pregnancy.
They help neurons grow, move and form connections, which is essential for communication in the brain. Thyroid hormones also support the development of brain structures and the production of myelin, the fatty coating that helps nerve signals travel quickly.
Thyroid disease — an umbrella term for conditions that affect the gland’s ability to produce hormones — is the second most common endocrine disorder among women of reproductive age.
When left untreated during pregnancy, thyroid problems have been linked to miscarriage, pre-eclampsia, premature birth, low birth weight and potential long-term effects on the child.
Yet in the US and many countries, routine thyroid testing isn’t part of standard pregnancy care, according to Paloma Health, a virtual clinic specializing in patients with thyroid conditions.
Doctors usually only check if a woman has risk factors — like a personal or family history of thyroid problems, autoimmune conditions or past pregnancy complications — or if she shows symptoms like fatigue, weight changes or a rapid heartbeat.
That leaves a lot of women flying under the radar. In fact, up to 60% of people with thyroid disease don’t even know they have it, according to the American Thyroid Association.
As a result, many moms-to-be may have untreated thyroid problems, which could put their child at a higher risk for autism.
“These findings underscore the need for routine monitoring and timely adjustment of therapy to maintain normal thyroid hormone levels throughout pregnancy,” Menashe said.
Untreated thyroid issues during pregnancy have also been linked to other neurodevelopmental disorders, like ADHD.
A large US study in 2020 found that children whose mothers had underactive thyroids with low hormone levels shortly before or early in pregnancy were 24% more likely to develop ADHD.
“Our findings make clear that thyroid health likely has a much larger role in fetal brain development and behavioral disorders like ADHD than we previously understood,” Dr. Morgan R. Peltier, a professor at NYU Long Island School of Medicine and the study’s lead author, said in a statement.
