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Can I Pass Hypothyroidism To My Baby?

Learn about the effects maternal hypothyroidism can have on a baby if left untreated.
Can I Pass Hypothyroidism To My Baby?

Medically Reviewed by:
Kimberly Langdon M.D.
Medically Reviewed by:

In this article:

  • Hypothyroidism and genetics
  • Will my baby be born with hypothyroidism?
  • Signs and symptoms of congential hypothyroidism
  • How to diagnose and treat congenital hypothyroidism
  • How to diagnose and treat maternal hypothyroidism


Hypothyroidism is one of the most common endocrine disorders, disproportionately affecting women. Indeed, one in eight women will develop a thyroid condition at some point in her life. 


Although hypothyroidism often develops after menopause (and is sometimes mistaken for menopause), women of childbearing age can also develop this condition. And, if you receive a diagnosis of hypothyroidism before or during pregnancy, you will need to take extra precautions to keep your baby healthy.


Hypothyroidism and genetics


The genetics of hypothyroidism are highly complex. 75% of patients with thyroid disease report that someone in their family has a thyroid disorder. While having a family member with a thyroid condition puts you at higher risk of developing hypothyroidism, there is no way to verify if hypothyroidism is genetic.


The most common cause of hypothyroidism is Hashimoto's thyroiditis. In this autoimmune disease, the immune system mistakenly attacks the thyroid gland. In Hashimoto's, chronic inflammation can eventually damage the tissues, leaving your thyroid unable to make sufficient thyroid hormone to support your metabolic needs. 


In cases where an autoimmune process causes hypothyroidism, there is likely a genetic component. Sometimes, even having other autoimmune conditions (like type 1 diabetes, lupus, or rheumatoid arthritis) can increase another family member's chance of having Hashimoto's thyroiditis—even if no one else in the family has it. 


Will my baby be born with hypothyroidism?


If a pregnant woman has low thyroid hormone, the baby may also be affected by hypothyroidism. Babies need thyroid hormones for average growth and development in utero, especially during the first few months of pregnancy. Suppose they do not get enough thyroid hormone. In that case, they can be born with irreversible symptoms, including impaired mental and physical development.


Thyroid dysgenesis

Congenital hypothyroidism is when a baby is born with a thyroid hormone deficiency. Most congenital hypothyroidism cases are from thyroid dysgenesis—meaning that the thyroid gland itself is missing or severely underdeveloped. If left untreated after birth, severe congenital hypothyroidism can lead to growth failure or permanent intellectual disability. 


Genetic disorders

Less frequently, genetic disorders can cause congenital hypothyroidism. Studies report gene mutations for sodium/iodide symporter, thyroid peroxidase (TPO), and thyroglobulin. Additionally, suppose a thyrotropin receptor blocking antibody (TRB-Ab) passes through the placenta. In that case, it may cause a temporary form of congenital hypothyroidism. 


Premature infants

Premature infants often have low thyroid hormone levels in the first few weeks of life due to several possible factors like the development of the hypothalamus-pituitary-thyroid axis, nutrition, or nonthyroidal illnesses. Research remains unclear whether treating premature infants with low thyroid hormone levels with thyroid hormone replacement medications improves neurodevelopmental outcomes.


What are the signs and symptoms of congenital hypothyroidism?


The symptoms of congenital hypothyroidism in the first week of life are not always obvious. However, if hypothyroidism is severe, symptoms may include:

  • Jaundice
  • Poor muscle tone
  • Feeding challenges
  • Swelling, especially around the eyes
  • Larger fontanelles
  • Excessive sleeping
  • Swollen tongue


If these symptoms are not treated shortly after birth, babies can suffer life-long consequences, including mental and physical impairments.


How to diagnose and treat congenital hypothyroidism?


Neonatal screening programs started in the 1970s and have significantly improved developmental outcomes for children born with congenital hypothyroidism. All of the hospitals in the United States screen for hypothyroidism using blood collected from your baby's heel before discharging from the hospital. 


If test results indicate an underactive thyroid, your baby's doctor will likely order another blood sample from a vein to confirm the diagnosis before beginning treatment.


Treatment is usually the same as hypothyroidism in adults. Babies with congenital hypothyroidism receive thyroid hormone replacement medication and often stay on it for the rest of their lives. 


Make sure to give your baby their thyroid hormone medication every day.  And schedule regular checkups with a pediatric endocrinologist to ensure your baby will have normal growth and brain development. Your doctor will test your child's thyroid hormones periodically to adjust medication dose as your child grows.


How to diagnose and treat maternal hypothyroidism in pregnancy?


Just as the impact of congenital hypothyroidism on a baby is profound, the effect of maternal hypothyroidism on pregnancy is as well. In the United States, maternal hypothyroidism is primarily due to Hashimoto's thyroiditis

Testing

Pregnant women with hypothyroidism usually need a thyroid blood test once a month during the first half of pregnancy. You may not need to test as often during the second half of pregnancy, especially if your thyroid levels are stable. It would be best if you worked closely with both your obstetrician and your endocrinologist.

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Treatment

Untreated hypothyroidism can lead to several complications like preeclampsia, low birth weight, premature separation of the placenta, or increased risk of miscarriage. Treatment with thyroid hormone replacement medication reduces the complications significantly.


The severity of the condition, onset and duration, and postnatal management influence a baby's brain development. Research suggests that even mild maternal hypothyroidism (from mild iodine deficiency, Hashimoto's thyroiditis, or too little medication) may affect fetal brain development


Additionally, iodine, a trace element, is required for the thyroid gland to produce thyroid hormones effectively. When thyroid-stimulating hormone (TSH) secretes from the pituitary, it increases the thyroid's uptake of iodine. Iodine stimulates the production and release of thyroid hormones thyroxine (T4) and triiodothyronine (T3). 


During pregnancy and lactation, iodine requirement increases, and the recommended intake goes up to 220 mcg and 290 mcg, respectively. Iodine does not occur naturally in the body, so supplementing with iodine before or early in pregnancy may increase the maternal T4 to provide the fetus with the proper amount of T4 for brain development. 

Medication dosage

Because estrogen levels can surge during pregnancy, women may require a higher than usual thyroid medication dose, especially in the third trimester. This is because estrogen can increase thyroxine-binding globulin, which determines how much free thyroid hormone is available for use in the body since the bound form is inactive.


Medication interactions

Prenatal vitamins are necessary for all pregnant women. However, suppose you take thyroid hormone replacement medication like levothyroxine or Synthroid. In that case, you will want to take your prenatal and medication separately. Certain minerals, like iron and calcium, can affect thyroid medication absorption.


A note from Paloma Health


Having hypothyroidism does not guarantee that your baby will also have hypothyroidism. Indeed, there is still speculation about the role genes play in hypothyroidism. Women with uncontrolled hypothyroidism during pregnancy can, however, pass complications onto their children. Fortunately, with good prenatal care and thyroid hormone replacement medication, most babies will be unaffected by hypothyroidism.

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