Hypothyroidism and Pregnancy: What Do You Need To Know?

Pregnancy causes significant changes in the levels of hormones created by the thyroid gland. For this reason, thyroid problems may sometimes start or worsen during or after pregnancy. The Thyroid gland produces T3 and T4 hormones, which regulate metabolism. 

When the thyroid gland becomes incapable of making sufficient thyroid hormones, this is termed as an underactive thyroid or hypothyroidism. 

The symptoms of hypothyroidism mimic the hormonal changes of a normal pregnancy and so can be easily overlooked. But if left untreated, hypothyroidism can be dangerous for both the mother and the baby. A pregnant woman's thyroid hormones are imperative not only for her but also for the baby’s development. 

pregnancy and hypothyroidism

What Are The Risk Factors For Hypothyroidism?

Women are at an elevated risk of hypothyroidism or an underactive thyroid before or during pregnancy if they are over the age of 30 years or have:

  • A family history of thyroid or an autoimmune disease
  • Preterm delivery or past infertility 
  • Current treatment with levothyroxine, a thyroid hormone drug, unless the dose is altered before or soon after conception
  • Prior radiation treatment of the neck or head
  • Thyroid antibodies, primarily thyroid peroxidase (TPO) antibodies, which are usually present in Hashimoto’s disease
  • Type 1 diabetes or other autoimmune diseases
  • Past thyroid surgery
  • A goiter (enlargement of the thyroid gland)


What Causes Hypothyroidism During Pregnancy?

The most common cause of underactive thyroid in pregnant women is Hashimoto’s disease, also known as Hashimoto thyroiditis. This is an autoimmune disease that occurs when your immune system forms antibodies that attack your thyroid. It causes the gland to produce too little thyroid hormone. People with this disease may or may not have any recognizable symptoms. 

Other causes of hypothyroidism during pregnancy include prior treatment for hyperthyroidism (a condition in which the thyroid gland produces excessive thyroid hormone), iodine deficiency, and surgery to eradicate thyroid tumours.

The thyroid may also become underactive after a pregnant woman has given birth to her child. Nearly seventy percent of women get postpartum thyroiditis in the first year after childbirth. This problem begins with hyperthyroidism, which usually elucidates without treatment in a couple of weeks or months. But sometimes, the inflammation results in hypothyroidism. In most cases, hypothyroidism gets recovered on its own. In countries where people do not take adequate iodine in the diet, iodine deficiency is the primary cause of hypothyroidism. The thyroid gland requires iodine to produce thyroid hormones. 

People living in the United States use iodized salt in their diet, so they don't lack iodine. However, pregnant or breastfeeding women require more iodine than usual and should raise their consumption of this vital mineral.


What Are The Symptoms Of Hypothyroidism?

Hypothyroidism may cause some of the following symptoms:

  • Weight gain
  • Tiredness
  • Depression
  • Constipation
  • Dry skin and hair
  • Irregular menses in women
  • Feeling cold

These symptoms are not specific to hypothyroidism. In fact, some of them are common in women. Your doctor may order a blood test to determine whether your symptoms are due to an underactive thyroid. Certain people with early or mild hypothyroidism may experience no symptoms. 


How Is Hypothyroidism Diagnosed?

To diagnose hypothyroidism, your doctor will take a physical exam and order blood tests to evaluate your thyroid hormone levels.

Thyroid-stimulating hormone, or TSH, is a hormone that stimulates the thyroid to produce T3 and T4 (also known as thyroxine). High TSH levels, in addition to low levels of T4, signify hypothyroidism. This happens when too little T4 in the blood prompts excess TSH to be manufactured as the body attempts to increase T4 levels. High TSH levels but normal levels of T4 signifies subclinical (early or mild) hypothyroidism.

If you have hypothyroid, you may require an antibody test to test for TPO antibodies. These abnormal antibodies will be present in the blood if Hashimoto's disease is the cause of your hypothyroidism.

Also Read: Iodine Deficiency Is Harmful For Health

Should Pregnant Women Get Screened For Hypothyroidism?

As pregnant women are highly susceptible to thyroid problems, they should have a thyroid function test even if they don’t experience any underactive thyroid symptoms. Preferably, this screening blood test should occur during the ninth month of pregnancy or at the first prenatal visit. 

Untreated thyroid disease can be hazardous, and so some experts recommend screening all newly pregnant women for abnormal thyroid function. Make sure you ask your healthcare specialist early in your pregnancy whether you require thyroid function blood tests.

Women who have known increased levels of TPO antibodies require additional thyroid function tests. They are at significant risk of developing hypothyroidism and pregnancy problems, including miscarriage. So, they should get a TSH blood test before they strive to become pregnant and again during the first and second trimesters of pregnancy.


What Treatment Options Are Available For Maternal Hypothyroidism?

The treatment for maternal hyperthyroidism includes thyroid hormone replacement with a form of T4 - levothyroxine. This medication is the same as T4 our body produces and is considered safe for pregnant women. 


Before Pregnancy

Your thyroid levels must remain normal before and during pregnancy. If you are already receiving levothyroxine to manage hypothyroidism, you should have your thyroid hormone levels tested before you attempt to conceive. If your TSH levels are very high, you may require an increment in your dose of levothyroxine. You should postpone pregnancy until your disease is well managed.


During Pregnancy

As soon as a hypothyroid woman gets pregnant, the levothyroxine dose usually must increase. The dose must probably increase by as much as 30% or even more in the first 4 - 6 weeks of pregnancy. Consult your doctor immediately after discovering that you are pregnant so that you can get a thyroid function blood test and talk over your treatment plan.

If you get hypothyroidism during pregnancy, you will require your T4 levels brought to normal as early as possible. Your healthcare specialist may prescribe increasing doses of levothyroxine until your T4 levels turn normal. After 30 - 40 days of starting the treatment, you should have your thyroid function tested again. Your thyroid function testing should also be done multiple times during pregnancy, generally every 4 - 6 weeks until delivery.


After Pregnancy

After childbirth, most hypothyroid women should decrease the levothyroxine dose they obtained during pregnancy.


What Can You Do To Have A Healthy Baby?

Work with your pregnancy care provider and your endocrinologist to receive adequate medical assistance before, during, and after pregnancy. An endocrinologist is a doctor who specializes in treating hormone-related problems. Take all the medications recommended and inform your doctor if you experience any side effects. 

To ensure you are getting enough iodine, take daily prenatal vitamins that incorporate 150 - 250 micrograms of potassium iodide or iodate. Breast-feeding women should supplement with 250 mcg per day of iodine to ensure that their breast milk supplies the iodine that their nursing babies require.

Remember, do not take thyroid medication along with any supplement or prenatal vitamins containing calcium or magnesium. These nutrients may interrupt the absorption of thyroid hormones. You can take these vitamins about 2-3 hours before or after taking your dose of levothyroxine.





Taylor Hill

Taylor writes for the Pregnancy and Baby Care section of the blog and has a knack for everything creative. She holds a Diploma of Medicine in Nursing & Paramedical and is known to add innovation in everything she does. An ardent lover of coffee, Taylor makes sure to go at a coffee tasting spree at least twice a month.