Thyroid Disease And Pregnancy
Symptoms, Diagnosis And Management Of Thyroid Disorders

Thyroid Disease In Pregnancy

Contents

• Overview
If You Develop Thyroid Disease In Pregnancy:
• What Are The Symptoms?
• How Is It Diagnosed?
• How Is It Treated?
• What Are The Dangers?
• What Causes Thyroid Disorders In Pregnancy?
• Can I Prevent It?
If You Already Have Thyroid Disease Before Pregnancy:
• Treatment Of Pre-Existing Conditions
• What Is Postpartum Thyroiditis?

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Thyroid Disease
Pregnancy Guide

Overview

Many women become pregnant with pre-existing thyroid conditions (although some are not aware they had a thyroid problem). While others develop it during pregnancy but find it disappears again after childbirth. Some changes in thyroid function are normal during pregnancy, but in some women pregnancy triggers full-blown symptoms of thyroid disease. Thyroid disease is where the thyroid gland produces either too much hormones (hyperthyroidism), or too little (hypothyroidism). If the condition is not managed properly it can have serious health consequences for both mom and baby. Even if you don't develop thyroid problems in pregnancy, the danger is not over after delivery. About 4 to 7 percent of women go on to develop temporary thyroid disorders in the first few months of childbirth. This is called postpartum thyroiditis. It usually disappears within a year but for some, the condition becomes permanent. Most women are not routinely screened for thyroid problems in pregnancy, so it is worth informing yourself about the signs and symptoms.

If You Develop Thyroid Disease In Pregnancy

What Are The Symptoms?

Have you been tired, moody and suffering from constipation lately? While these are all common pregnancy symptoms, they are also indications of thyroid disease.

Signs of hypothyroidism (occurs in about 3 to 5 of every 1,000 pregnancies) include:
• Feeling very tired.
• Feel the cold more than other people.
• Dry skin and a puffy looking face.
• Constipation in pregnancy.
• Depression.
• Swelling of the hands and feet.
• Memory loss.
• Muscle aches and pains.
• Pregnancy cramps.

Hyperthyroidism is less common in pregnancy (occurs in about 2 in every 1,000 pregnancies) but signs include:
• Weight loss (or difficulties gaining weight). This is the biggest clue.
• Insomnia.
• Fatigue.
• Goiters - enlarged swelling in the neck.
• Rapid heartbeat or heart palpitations.
• Warm skin and more prone to feeling hot.

How Is It Diagnosed?

A simple blood test to check your thyroid hormone levels (TSH and T4 hormones) will help doctors discover if there is a problem. Yet, while thyroid tests usually give an accurate result for non-pregnant women, they can be more difficult to interpret in pregnancy. This is because pregnancy hormones can throw the results off kilter. For this reason, a physical examination is important. Your doctor will look for signs of swelling of your thyroid gland, if there are any skin changes and he will listen to your heart rate. While some symptoms, such as irritability, fatigue and increased heart rate are also common symptoms of pregnancy, others are more closely associated with hyperthyroidism, specifically: weight gain, morning sickness and a severe type of nausea called hyperemesis gravidarum. The symptoms of hypothyroidism on the other hand, including dry skin and proneness to feeling the cold, are far less specific. If you have type 1 diabetes this raises your risk factors for hypothyroidism.

How Is It Treated?

Hypothyroidism
There are no clearly defined rules as to when a mother should be treated for hypothyroidism in pregnancy - it depends on how mild or severe the condition is. Usually if the TSH blood test result comes back with a level of 4 or over, treatment is considered appropriate. She will be prescribed a hormone replacement tablet called thyroxine and will have a blood test carried out every 6 to 8 weeks to ensure she is on the right dosage. Synthetic thyroxine is considered safe for the baby. If a mother's TSH level is between 2 and 4 but she also tests positive for antibodies confirming Hashimoto's disease, she should probably also receive medication. Fortunately studies show that mild cases of hypothyroidism which were not detected in the early stages of pregnancy, do not appear to harm the fetus.

Hyperthyroidism
Mild cases (where tests show the TSH levels are high but T4 levels are normal) are usually not treated. More severe cases are treated with antithyroid medications: propylthiouracil (PTU) in the first trimester and switched to methimazole (Tapazole and Northyx) for the remainder of the pregnancy. These work by reducing the amount of thyroid hormones produced. Most women who become hyperthyroid while pregnant are diagnosed with Graves disease, a type of autoimmune problem.

Prognosis: With both conditions, after the birth of their child, most women’s thyroid function returns to normal. If they have been taking pills to control symptoms, they should be able to stop taking them again.

What Are The Dangers?

Uncontrolled thyroid disorders during pregnancy can cause:
• Preeclampsia.
• Miscarriage (see, what are the signs of a miscarriage?)
• Bleeding after delivery.
• Anemia in pregnancy.
• Intrauterine growth restriction.
• Stillbirth, death of the fetus after week 20 but before labor.
• Congestive heart failure in the mother, but this is rare.
• Thyroid storm - a sudden and severe worsening of hyperthyroidism.

What Causes Thyroid Disorders In Pregnancy?

There are many different causes of thyroid disease, the most common being:
• Graves disease, the most common cause of hyperthyroidism.
• Hyperemesis gravidarum, severe morning sickness.
• Hashimoto's disease, the main cause of hypothyroidism.

Can I Prevent It?

There is no known way to prevent thyroid disease; however you can reduce your chances of developing it by preparing for pregnancy in advance. Ensure your body is fit and strong by following a healthy eating plan and taking daily exercise for at least 3 months before falling pregnant. When you become pregnant, talk to your pregnancy healthcare team about taking an iodine supplement. Iodine is an important mineral for maintaining a healthy thyroid, and most pregnant women need an additional 250 micrograms a day. Choosing iodized table salt and prenatal vitamins containing iodine will ensure this requirement is met.

If You Already Had Thyroid Disease Before Pregnancy

If you have already been diagnosed with a thyroid disorder before falling pregnant, and are taking treatment for your condition, you will need to discuss your ongoing requirements with your doctor. Ideally you should have your condition under control before becoming pregnant. This will reduce your risk of complications like miscarriage and bleeding after delivery. Even if you previously had a thyroid disorder which has since cleared up, you need to be aware that it may return during pregnancy. Your doctor should screen you once a month for signs of a recurrence.

Treatment Of Pre-Existing Hyperthyroidism
If you were taking medications before pregnancy, you will probably be switched to PTU and your thyroid levels will be monitored on a monthly basis. Beta blockers to control tremors and palpitations may be prescribed if needed. They can be stopped once the hyperthyroidism is controlled. If you plan on breastfeeding your baby, it is safe to continue taking PTU - much lower amounts of it will pass into your breast milk than if you were taking Tapazole. Your baby's thyroid function however should be periodically checked. The postpartum period, particularly the first 3 months can be challenging, as typically Graves disease can worsen in this period. Higher doses of your thyroid medications may be necessary for this time.

Treatment Of Pre-Existing Hypothyroidism
The treatment for non-pregnant women and pregnant women is the same - if you were taking levothyroxine before, you will continue to do so in pregnancy. Your doctor may however prescribe a higher dose (25 to 50 percent more) in order to keep your TSH levels stable. Ideally you should have your dose doubled just before becoming pregnant. Your doctor will recommend having your TSH levels measured every 4 weeks throughout your pregnancy to ensure the dosage is correct. As soon as you deliver your baby, you can usually go back to your pre-pregnancy dosage. It should be noted that prenatal vitamins can impact on the amount of levothyroxine your body absorbs, so be sure to take them at different times of the day (at least 2 to 3 hours apart).

Interesting Fact
Because pregnant women undergo so many examinations, scans and tests, their doctors often discover the presence of thyroid nodules - small lumps which may or may not be visible to the eye. In fact these lumps are discovered in 10 percent of pregnant women. While 95 percent are harmless they should still be biopsied for signs of thyroid cancer.

What Is Postpartum Thyroiditis?

This is where a woman who previously had no signs of thyroid problems discovers that her thyroid becomes inflamed after childbirth. Initially she may develop symptoms of hyperthyroidism such as weight loss and feeling hot, but then it can swing the other way and she develops signs of hypothyroidism (weight gain and feeling cold). Usually the symptoms are mild and do not require treatment. It is more common in women with type 1 diabetes or a family history of thyroid problems. It typically occurs 4 to 8 months after childbirth and can last up to 18 months before the thyroid returns to normal. In 20 percent of cases, the women will remain permanently hypothyroid.

Related Articles on Thyroid Disorders During Pregnancy

For more useful information, see the following:

• Prenatal Care Guide : Mom and baby welfare advice.

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