Maternal Hypothyroidism And Fetal Brain Development

Maternal Hypothyroidism and Fetal Brain Development

Thyroid hormones play a critical role in fetal brain development. The fetus depends entirely on maternal thyroid hormones for the first 12 weeks of pregnancy, until the baby’s thyroid begins to produce thyroid hormones on its own. For the first trimester the baby is completely dependent on the mother for thyroid hormones necessary for brain development. Babies born to mothers with undiagnosed or inadequately treated hypothyroidism are at risk for lower IQ scores and learning disabilities. Despite the mounting evidence, thyroid screening is currently NOT mandatory in pregnancy. It is SHAMEFUL that countries around the world do not set health policies to protect our babies.

Thyroid screening should be required for every pregnant woman worldwide.

Thyroid Screening in Pregnancy

In a 1999 study published in The New England Journal of Medicine, researchers recruited women who had tested positive for hypothyroidism during pregnancy as determined by a high TSH level, along with a control group of women with normal TSH levels. Their 7 to 9  year old children at the time of the study underwent 15 tests related to intelligence, attention, language, reading ability, school performance, learning problems, and visual-motor performance. The children were grouped according to whether their mother’s hypothyroidism had been treated during the pregnancy. Researchers discovered:[1]

“The larger deficits in performance were found among the children of the untreated women; their scores for all 15 tests were worse than those of the control children. Their average full-scale IQ score on the Wechsler Intelligence Scale for Children, third edition, was 7 points lower, and 19 percent of the children of women with hypothyroidism had an IQ score of 85 or lower, compared with 5 percent of the control children.

The current study shows that hypothyroidism in pregnant women can adversely affect their children’s subsequent performance on neuropsychological tests. Decreases in performance can occur even when the the pregnant woman’s hypothyroidism is mild and probably asymptomatic.”

Given the growing body of scientific evidence showing the dangers of maternal hypothyroidism on fetal brain development, why is thyroid screening not mandatory for every pregnant woman worldwide? Why take chances with our babies?

The Endocrine Society

According to the Endocrine Society “Management of Thyroid Dysfunction during Pregnancy and Postpartum” clinical practice guidelines:[2]

Recommendation #1:

Both maternal and fetal hypothyroidism are known to have serious adverse effects on the fetus. Therefore maternal hypothyroidism should be avoided. Targeted case finding is recommended at the first prenatal visit or at diagnosis of pregnancy.

 Wait…Rewind…Targeted Case Finding For Hypothyroidism?

The Thyroid Federation International estimates there are up to 300 million people worldwide with thyroid dysfunction, majority women, yet over half are unaware of their condition. Over 150 million thyroid sufferers remain undiagnosed worldwide. They have no clue and clearly their doctors have no clue. With targeted case finding, many pregnant hypothyroid women will continue to fall though the medical cracks and their babies will be in danger.

American Thyroid Association

According to the Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum:[3]

Recommendation 72:

There is insufficient evidence to recommend for or against universal TSH screening at the first trimester visit.

The president of the American Thyroid Association, Dr. Kenneth D. Burman, was quoted in The New York Times 2009 article Prenatal Testing of Thyroid Is Debated:

For now, medical societies advise testing only high-risk women.

As a matter of policy, Dr. Kenneth D. Burman, the president of the American Thyroid Association, agrees with that stance for now. Yet like more and more endocrinologists, he offers T.S.H. pregnancy testing in his practice, at Washington Hospital Center in Washington.

“Every patient I see who’s considering getting pregnant or is pregnant gets a thyroid function test,” he said. “And I think that’s the right thing to do.”

The President of the American Thyroid Association stated that he tests every patient considering getting pregnant or is pregnant. WAIT!! What about all the doctors who don’t know this? What about all the doctors in the world who don’t test their pregnant patients? What happens to their babies? The medical societies are playing a very risky game with our babies. I for one will fight like a warrior to ensure a change in health policy to mandate thyroid screening in pregnancy. I won’t rest until this happens.



1. Haddow, J.E. et al. Maternal Thyroid Deficiency During Pregnancy And Subsequent Neuropsychological Development Of The Child. The New England Journal of Medicine, 1999 Aug 19; 341(8):549-555.

2. Endocrine Society. Management of Thyroid Dysfunction during Pregnancy and Postpartum: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism, 2007 August; 92(8)(Supplement):S1-S47.

3. Stagnaro-Green, A. et al. Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum. Thyroid, 2011 October; 21(10): 1081-1125.

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About Dana Trentini

Dana Trentini founded Hypothyroid Mom October 2012 in memory of the unborn baby she lost to hypothyroidism. This is for informational purposes only and should not be considered a substitute for consulting your physician regarding medical advice pertaining to your health. Hypothyroid Mom includes affiliate links including the Amazon Services LLC Associates Program.


  1. Hello Dana,
    I was diagnosed with hypothyroidism since I was 18. I am 35 years old and 15 weeks pregnant. unfortunately I passed my first 12 weeks of pregnancy with 4.50 TSH level. My Doctor increased my Synthroid dosage to 88 mg and I did another screen test last week and my TSH was 3.75 which was out of pregnancy range. I am worried about my baby’s brain development and IQ level now that I have passed the first 15 weeks of my pregnancy with out of range TSH. Please let me know what do you think? Is that already late ?

    • sounds like baby starts making its own after 12 weeks – see if you can find that online like I just did (don’t remember the site)

      • hopefully, the lower second number might indicate baby is making its own (b/c I think TSH is a measure of the “demand” on the thyroid based on presence/absence of thyroid stimulating hormone – less of that, more production is going on, i believe) – but your doctor s/b your best resource in your particular instance – a good question to call in to his office b/c you need to know – meanwhile, learn all you can on the basics of thyroid and esp. during pregnancy – and, of course, make sure you bring your concern also to your prayer life b/c God cares – get the doctor’s office to recommend some reading for you, as well

    • Hi Molood,
      How is your child?
      Kind regards,

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