Hypothyroidism in Pregnancy: Treatment, Prevention, and Tests

Hypothyroidism is an endocrine condition in which your thyroid gland doesn’t produce enough T3 (triiodothyronine) and/or T4 (thyroxine). It’s also known as underactive thyroid.

Thyroid disease in pregnancy is uncommon (3-5 occurrences per every 1,000 pregnancies). Even if you didn’t deal with diagnosed thyroid issues before conception, it’s possible to develop maternal hypothyroidism. 

2-3% of women have subclinical hypothyroidism even before becoming pregnant, marked by elevated TSH (thyroid-stimulating hormone) but T3/T4 levels within range. 

Although this is not considered as serious as full-blown hypothyroidism, subclinical hypothyroidism during pregnancy may still cause concerns to both mother and fetus.

18% of pregnant mothers test for the presence of thyroid peroxidase antibody (TPOAb) or thyroglobulin antibody (TgAb). These antibodies signal thyroid dysfunction may be present.

Can I have a healthy pregnancy with hypothyroidism? You can have a healthy pregnancy with hypothyroidism with proper management of your condition (thyroid medication) and having your levels of thyroid hormones regularly tested.

Let’s take a look at how hypothyroidism and pregnancy interact and what to do about it.

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What is the thyroid?

Your thyroid is a small gland shaped like a butterfly located at the front of your neck. As an important part of your endocrine system, this gland produces and releases hormones.

Your thyroid’s main job is to control the speed of your metabolism (the breakdown of food into energy in your body).

When your thyroid isn’t working properly, it can impact how your entire body functions.

Symptoms Of Hypothyroidism

The symptoms of hypothyroidism in pregnancy include:

• Weight gain (also a common sign of pregnancy)
• Fatigue
• Slow heart rate
• Hoarseness
• Snoring
• Joint pain
• Muscle aches, tenderness, stiffness, and weakness
• High cholesterol
• Cold hands and feet
• Constipation
• Brittle nails
• Thinning hair, eyebrows
• Dry skin
• Impaired memory, trouble concentrating
• Enlarged thyroid (goiter)

All of these symptoms present themselves in hypothyroidism outside of pregnancy. If your body doesn’t produce enough thyroid hormones, these will be the first signs you’ll need testing.

Is there a cure for hypothyroidism? Yes, there is a cure for a majority of cases of hypothyroidism caused by Hashimoto’s (Hashimoto’s thyroiditis). Patients may completely reverse hypothyroidism with an individualized treatment plan, including dietary changes, supplements, stress relief, peptide therapy, and thyroid medications.

Thyroid Conditions in Pregnancy

There are 3 primary thyroid conditions (all of which can occur during pregnancy):

1. Hypothyroidism: This causes your body’s functions to slow down due to underactivity of your thyroid. Hypothyroidism during pregnancy is usually caused by an autoimmune disorder called Hashimoto’s disease. This autoimmune thyroid disease causes your immune system to create antibodies that attack your thyroid and damage it, so it can’t produce thyroid hormones properly.
2. Hyperthyroidism: This occurs when the thyroid is overactive and produces too much thyroid hormone. Graves disease (an autoimmune disorder) is the leading cause of hyperthyroidism in pregnancy. In rare cases, hyperthyroidism is linked to a severe form of morning sickness called hyperemesis gravidarum (excessive nausea and vomiting during pregnancy). In pregnancy, hyperthyroidism is often treated with methimazole or propylthiouracil.
3. Secondary hypothyroidism: This is far less common (about 1 in 1,000 cases) and is caused by a malfunctioning pituitary gland, frequently due to a tumor. A malfunctioning pituitary gland that doesn’t produce enough TSH (thyroid-stimulating hormone) leads to hypothyroidism.

Hypothyroidism may have no adverse effects on your pregnancy if you manage your health well.

How will hypothyroidism affect my baby?

Complications of maternal hypothyroidism for a newborn child, especially when untreated in the mother, can last far into childhood. 

Preeclampsia (caused by high blood pressure and thyroid problems) is one of the biggest concerns for mother and baby during pregnancy. It can cause poor blood flow to the placenta, typically beginning in the second trimester.

The most common risks of untreated hypothyroidism for the baby include:

• Low birth weight
• Premature birth
• Stillbirth
• Neonatal death (death shortly after delivery)
• Poor hippocampal development
• Infantile myxedema (a rare disorder associated with severe hypothyroidism that can cause dwarfism, intellectual abnormalities, and other health concerns)
• Poor nervous system development
• Memory problems
• Learning disabilities
• Increased risk of autism
• Issues with visuospatial processing (the ability to interpret what the eyes see)
• Problems with motor skills
• Cyclic vomiting syndrome
• Attention problems similar to those seen in ADHD

Does hypothyroidism cause birth defects? According to the best evidence available, hypothyroidism in pregnancy does not cause birth defects more often than in a typical pregnancy.

How does thyroid function impact the mother and baby during pregnancy? During the first 18-20 weeks of pregnancy, a fetus does not produce its own thyroid hormone and relies on the mother for it.

Is hypothyroidism considered a factor for high-risk pregnancy? Hypothyroidism does not necessarily mean you have a high-risk pregnancy unless the condition is untreated. As long as you consume plenty of iodine-rich foods or take iodine in your prenatal vitamins, maternal hypothyroidism isn’t typically a cause for concern. 

Sometimes, your doctor may prescribe medications like levothyroxine (depending on the severity of the thyroid condition). 

Levothyroxine is safe to take during pregnancy if prescribed by your healthcare provider.

Testing the Thyroid

There are a few tests that your OB/GYN or endocrinology specialist may run if you are at risk for hypothyroidism. Your doctor should monitor your thyroid hormone levels every 4 weeks during the first half of your pregnancy.

Standard blood tests for hypothyroidism include thyroid-stimulating hormone levels (TSH) and free T4 levels. When TSH levels exceed 2.5 mIU/L during pregnancy, your doctor may prescribe pharmaceutical treatment, especially if TPO antibodies are present. 

When TSH levels exceed 10 mIU/L, you’ll probably need to take medication throughout the rest of your pregnancy.

Standard vs. Functional Hypothyroidism Screening

As our understanding of maternal hypothyroidism grows, a more robust set of thyroid function tests may help to paint a fuller picture of your thyroid function. 

To screen, diagnose, and treat maternal hypothyroidism, a functional medicine provider may test your:

• TSH levels
• Free T4
• Free T3
• Total T4 levels
• Total T3
• Reverse T3
• Anti-thyroglobulin and anti-TPO antibodies (Hashimoto’s thyroid antibodies)
• Thyroid-binding globulin (TBG level)

Who is at risk for maternal hypothyroidism?

Patients at risk for maternal hypothyroidism have any of the following risk factors:

• Current treatment of hypothyroidism with levothyroxine, unless the dosage is adjusted before conception
• A goiter and/or thyroid nodules
• Over 30 years old
• Pre-existing iodine deficiency
• Past infertility
• Past preterm delivery
• Maternal hypothyroidism during a previous pregnancy
• Previous child with a thyroid disorder
• Family history of thyroid disease (including Graves’ disease or Hashimoto’s) or another autoimmune disorder
• Type 1 diabetes
• Celiac disease
• Levels of certain bacteria in the oral and gut microbiome
• Prior radiation exposure to the neck
• Thyroid cancer
• Previous thyroid surgery

The causes of hypothyroidism are unclear, as it’s a multifactorial condition. However, iodine deficiency is one of the most common causes.

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Treatment for Maternal Hypothyroidism

Depending on your provider and the severity of your hypothyroidism, treatment for an underactive thyroid in pregnancy may include medication, dietary changes, and supplements.

While hypothyroidism in pregnancy can cause serious complications, it’s important to consider the risks of overtreatment and undertreatment when it comes to maternal hypothyroidism.

Who should be treated for hypothyroidism in pregnancy? Women with serum TSH levels greater than 10 mIU/L during the first trimester of pregnancy should be treated for hypothyroidism. When TSH levels are under 2.5 mIU/L, levothyroxine treatment is not required. 

If thyroid testing finds a TSH level between 2.5-10 mIU/L, your doctor may prescribe medication to treat your hypothyroidism, especially if you also have TPO or anti-TG antibodies.

Standard treatments for managing maternal hypothyroidism include:

• Increasing thyroid medication dosage
• Following a hypothyroidism diet
• Taking high-quality prenatal vitamins

Your provider will help you determine the potential side effects and weigh the benefits vs. drawbacks of each treatment.

Medications

Your OB/GYN may determine you need thyroid hormone replacement in the form of prescription drugs to manage maternal thyroid conditions. Medications that may manage symptoms of hypothyroidism in pregnancy include:

• Levothyroxine (Synthroid)
• Liothyronine (TrioStat)
• Liotrix (Thyrolar)

Diet Changes

To follow a hypothyroidism diet during pregnancy:

• Eliminate items from your diet that can trigger autoimmune responses, including alcohol, excess sugar, gluten, dairy, soy, artificial sweeteners, and processed foods.
• Fill your plate with nutrient-dense, calorie-rich foods. When possible, opt for organic, whole foods.
• Eat iodine-rich foods like seaweed, eggs, organic grass-fed & fermented dairy, and kelp. As iodine deficiency is a common cause of maternal hypothyroidism, so getting plenty of this nutrient will improve your chances for an ideal pregnancy outcome.

In typical hypothyroid patients, our first-line approach is to start an autoimmune Paleo diet (also known as the AIP diet).

Unfortunately, this isn’t a great idea for pregnant moms — it’s difficult on AIP to get enough calories and nutrition to grow your new human.

If you still struggle with hypothyroidism after delivery, talk to your doctor or dietician about temporarily following an AIP diet to identify your dietary triggers.

Natural Hypothyroid Supplements

It’s essential to take prenatal vitamins to support a healthy pregnancy. To address potential underactive thyroid concerns, your prenatal vitamin should contain selenium and iodine. Combining these with myo-inositol may help to treat and even prevent maternal hypothyroidism.

Look for a prenatal vitamin that includes the following:

• Iodine
• Vitamin D3
• Zinc
• Magnesium
• Selenium
• B vitamins, especially Methyl-Folate (aka 5MTHF)
• Vitamin K2

It’s also essential to take high quality Omega-3 fish oils with adequate DHA and EPA along with your prenatal vitamins. These fatty acids are critical for your baby’s brain and nervous system development.

Many supplements aren’t known to be safe during pregnancy, including several supplements that we recommend to hypothyroid patients. Always talk to your doctor before starting a new supplement regimen, especially if you’re pregnant or trying to conceive.

Important: When taking a prenatal supplement containing iron (which helps with anemia) and/or calcium, leave at least 2-4 hours between this vitamin and levothyroxine (or other thyroid medication). These nutrients can impair the absorption of thyroid hormones in your gut.

Postnatal Treatment for Hypothyroidism

If you developed hypothyroidism after getting pregnant, you may be able to discontinue taking thyroid medication once your baby is delivered.

If you had hypothyroidism before conceiving, you’ll likely be able to return to your pre-pregnancy thyroid medication dosage based on postnatal TSH levels. However, always follow your doctor’s orders — sometimes, your TSH won’t regulate until after you’re finished breastfeeding.

Children of people who develop maternal hypothyroidism are more likely to develop thyroid dysfunction later in life. Keeping their iodine consumption at a normal level will help with prevention.

Continue taking 250 micrograms or more of iron each day while breastfeeding.

Can I breastfeed with hypothyroidism? You can breastfeed with hypothyroidism. It’s safe and recommended for both mother and baby. Talk to your doctor if you’re concerned about any risks of breastfeeding and an underactive thyroid.

Newborn babies are susceptible to underactive thyroid. Fortunately, all 50 US states require universal screenings for hypothyroidism at birth. If newborns are left untreated, congenital hypothyroidism can lead to slow brain development.

Hypothyroidism in pregnancy should be closely monitored, but proper treatment will allow you to have a healthy pregnancy and birth.

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