Hypothyroidism in Pregnancy: Causes, Symptoms & Effects

Hypothyroidism in pregnancy is the most common thyroid disorder for pregnant women. In pregnancy, a normal pregnant woman will experience hormone changes in her body as well as the thyroid gland size to cope with increased demand- a growing baby in the womb. The increase of thyroid hormone demand not only cope with the mother’s metabolic needs also the growing child. Thyroid hormone is important for the baby’s brain development and growth, especially in the first trimester.

The increased demand for thyroid hormone is to accommodate the growing baby’s need for the first 20 weeks of pregnancy, as he/she solely depends on the mother for the thyroid hormone before he/she can produce on its own. Usually, a healthy thyroid gland from a healthy woman can support both the mother and the baby’s needs. If the mother is unable to produce enough thyroid hormone for both, this condition is called hypothyroidism.

Insufficient thyroid hormone will cause some complications and health issues to both mother and the child, which we will explain later in this article. Therefore, it is important to instill awareness about hypothyroidism in pregnancy, causes, symptoms, harmful effects, and treatment to prevent any undesired outcomes.

Hypothyroidism in Pregnancy

Hypothyroidism in Pregnancy – Symptoms

Knowing our thyroid status during pregnancy is important. Women who are hypothyroidism, have similar symptoms of pregnancy, you may overlook and get untreated if you are not aware.

If there is not enough thyroid hormone produced to support both mother and child, some bodily functions can be affected. Here are the signs which indicate thyroid hormone insufficiency such as:

  1. Fatigue
  2. Inappropriate gain of body weight
  3. Constipation
  4. Sensitive to cold
  5. Slow heart rate (< 60/bpm)
  6. Increase blood pressure
  7. Dry skin and hair loss
  8. Poor memory and focus
  9. Depression

It can go undetected if some women may have mild to no symptoms. Often thought that mild symptoms like fatigue, weight gain, and constipation are part of the feature of pregnancy. If you have a slow heart rate, sensitive to cold, and are accompanied by other 3 or more signs mentioned above, you are at a higher risk of getting hypothyroidism. Seek medical help and get tested immediately.

If you have a family history of hypothyroidism, or you have a personal history of miscarriage, preterm delivery, type 1 diabetes, or other autoimmune diseases, you are at a higher risk of getting hypothyroidism and you should go for thyroid functioning screening.

Causes of hypothyroidism in Pregnancy

Some women are unable to produce enough thyroid hormone with underlying conditions. We have listed down a few common causes of hypothyroidism in pregnancy:

1. Iodine deficiency

Iodine is essential to make thyroid hormone. Insufficient iodine intake will cause insufficient thyroid hormone production. Because iodine intakes in pregnancy are currently low in the United States, the American Thyroid Association (ATA) recommends that US women who are planning to become pregnant, who are pregnant, or breastfeeding, should take a daily supplement containing 150 mcg of iodine to avoid deficiency. For those iodine-sufficient regions, hypothyroidism in pregnancy can be caused by an autoimmune disorder.

2. Autoimmune disorder

Women who have autoimmune disorders such as Hashimoto’s thyroiditis, destruction of thyroid gland cells by own body immune system. What causes the own immune system to attack is still not clear but experts believe it may be due to factors like genetic and environmental triggers such as stress or exposure to radiation. This disease can result in low thyroid hormone production.

3. Women who have undergone treatment for Graves’ disease

Graves’ disease is an autoimmune disease that leads to the overactivity of the thyroid gland causing hyperthyroidism. Overtreatment of hyperthyroid women with anti-thyroid treatment may cause them to become hypothyroidism.

The harmful effect of hypothyroidism in pregnancy

Impact on the mother

Women with hypothyroidism are found to be less fertile, even if they conceive, the risk of miscarriage is high. The risk of getting other health complications during pregnancy such as gestational hypertension, anemia, stillbirth, premature separation of placenta and uterus (abruptio placenta), and postpartum bleeding is high too. These complications can threaten your life as well as your baby.

Some women who have a healthy thyroid gland may develop postpartum thyroiditis (PPT), which lasts for 12 months after childbirth. It may be due to some women who have underlying autoimmune conditions that flare after childbirth as a result of fluctuation of immune function. PPT is hard to diagnose as it often has similar symptoms to postpartum depression caused by the stress from childcare. Therefore, it is important to know your thyroid status if you are at a higher risk group – with a family history or personal history of autoimmune diseases.

Impact on the baby

Thyroid hormone is critical for a baby’s brain growth and development. A baby depends on his/her mother’s thyroid hormone for the first 20 weeks of pregnancy before the baby can produce on its own. Untreated severe hypothyroidism mother will impair brain development in the baby. Even a mother with mild symptoms will have mild abnormalities in the baby’s brain development.

Several studies have found that children who are born to mothers with hypothyroidism, will have problems in learning abilities than other normal children.

With early detection and treatment for the mother, these developmental abnormalities can be prevented.

Treatment for women with hypothyroidism in pregnancy

Medication treatment is found to be safe for pregnant women who are hypothyroidism. Giving Levothyroxine, a synthetic form of your thyroid hormones is an effective treatment for pregnant women. The thyroid function will usually become normal after the treatment.

Levothyroxine and prenatal vitamins should not be taken at the same time and should be separated by at least 4 hours. Prenatal vitamins contain iron and calcium that can impair the absorption of thyroid hormone from the gastrointestinal tract.

As a conclusion

Hypothyroidism in pregnancy will bring a huge harmful impact to the mother and the unborn baby and it has been proven can impair the baby’s brain development during the first 3 months if a hypothyroid mother gets untreated. This is preventable and simple treatment can help to prevent undesired outcomes.

It is important to let all the expecting mothers understand the role of the thyroid in maintaining the mother’s good health as well as the baby throughout the pregnancy.

Note: This article is only for general knowledge, it can not be used to supersede any professional health advice.

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