Hypothyroidism in pregnancy affects around 2-3% of pregnancies, but in most cases it is subclinical.  Here we take you through everything you need to know about hypothyroidism in pregnancy.

What is hypothyroidism?

The thyroid is a gland shaped like a butterfly found at the front of your neck. It makes hormones which control your body’s use of energy. As such, these hormones affect how all of the other systems in your body work.

If you have too little of the thyroid hormone then this is called hypothyroidism. This occurs in people who aren’t pregnant too, but hypothyroidism in pregnancy is specifically when your thyroid in underactive while pregnant.

Thyroid hormones and pregnancy

Thyroid hormones aren’t only needed by the pregnant woman to enable her body to function well. They are needed for the baby’s development too. It takes until around 18-20 weeks for the baby’s own thyroid to be working sufficiently, without mum’s thyroid supplying the hormones for them.

It’s very normal for the thyroid gland to become slightly bigger in pregnancy and for you to have higher amounts of thyroid hormones. Pregnancy hormones cause this. Because of this, and because of many symptoms of hypothyroidism mimicking other symptoms of pregnancy, it can be tricky to spot thyroid problems. Hypothyroidism is generally easier to spot in pregnancy than hyperthyroidism.

Symptoms of hypothyroidism in pregnancy

It can be tricky, because symptoms of hypothyroidism may seem like normal pregnancy symptoms. Symptoms of hypothyroidism in pregnancy include:

• Extreme fatigue and tiredness
• Often feeling very cold
• Muscle cramping
• Constipation
• Cognitive problems, such as difficulties concentrating and remembering things
• Weight gain
• Dry skin and hair thinning, including the loss of eyebrows
• Shortness of breath during activity
• Carpal tunnel syndrome

It’s also possible to have hypothyroidism during pregnancy and not have any notable symptoms at all.

The causes of hypothyroidism in pregnancy

The most common cause of hypothyroidism in pregnancy is Hashimoto’s disease. This is an autoimmune disorder in which your antibodies start to mistakenly attack the thyroid gland, causing it to become inflamed and less able to generate thyroid hormones.

Is hypothyroidism in pregnancy dangerous?

Unfortunately, untreated hypothyroidism can cause a number of complications with the pregnancy. It is associated with preeclampsia – a dangerous rise in blood pressure late in the pregnancy which can be harmful to both mother and child. It’s also associated with a higher risk of miscarriage earlier on in pregnancy, as well as stillbirth. It can sometimes cause anemia as well as low birthweight. Very rarely it may cause congestive heart failure. There may also be issues with the baby’s brain development.

Bear in mind that these concerns are most typically associated with extreme and untreated hypothyroidism. It’s for this reason that diagnosing hypothyroidism in pregnancy is essential, allowing timely and appropriate treatment.

Diagnosing hypothyroidism in pregnancy

Hypothyroidism in pregnancy is easy to pick up from a blood test which measures the amount of thyroid hormones in your blood. In addition, the blood test may be used to study the antibodies associated with Hashimoto’s disease.

Treating hypothyroidism in pregnancy

Fortunately, it is relatively easy to treat hypothyroidism in pregnancy. The most common treatment is levothyroxine. This medication is a synthetic form of the thyroid hormone, T4 and replaces the hormones that you’re currently unable to make. It’s safe for you and your baby.

During pregnancy, it is strongly recommended that you take synthetic thyroid treatment like levothyroxine, rather than natural sources (such as Armour Thyroid). Natural thyroid treatments can be very useful in other cases of hypothyroidism, precisely because they contain more T3. However, your developing baby’s brain cannot take on T3 in the way it can take on T4, so levothyroxine is best.

If you already had a diagnosis of hypothyroidism before getting pregnant then it may be necessary to increase the dose you take of levothyroxine.

It’s important that your thyroid hormone levels are regularly checked during the pregnancy, especially during the first 4-5 months. You should expect blood tests around every 4-6 weeks. This allows your healthcare team to adjust the dose of your levothyroxine appropriately.

Does hypothyroidism go away again after birth?

It’s relatively usual for hypothyroidism in pregnancy to linger for up to a year after the baby is born. Some women with hypothyroidism in pregnancy will go on to have longer term thyroid problems. If you’ve had hypothyroidism in pregnancy, and even those who haven’t, you may develop postpartum thyroiditis.

With postpartum thyroiditis, your thyroid gland is responding to the changing hormones after birth. It causes the thyroid gland to become inflamed. In the first instance, this often means you have too much thyroid hormone in your bloodstream, causing hyperthyroidism. This may last for around 3 months. Then, due to the inflammation, the opposite happens, and you have too little thyroid hormone, causing hypothyroidism. As said, this usually lasts for up to a year, but may never return to normal. You may have both hyperthyroidism and hypothyroidism after birth, or only one.

Due to postpartum thyroiditis commonly affecting those who experienced hypothyroidism in pregnancy, it’s essential for women with Hashimoto’s disease to be regularly monitored during the post-partum period. During this time, changes to thyroid medications and doses are common.

Be aware of the symptoms of both hyperthyroidism and hypothyroidism so that you can raise any concerns with your doctor. During the hyperthyroidism stage, you may not need treatment, if symptoms are mild or not noticeable. However, during the hypothyroidism stage, you are more likely to need treatment.

Can I breastfeed if I am taking thyroid treatment?

During the hyperthyroidism stage of postpartum thyroiditis, you may be prescribed beta-blockers to control your heart rate. Ask to be prescribed ones which are safe for use while breastfeeding.

In terms of hypothyroidism treatments like thyroxine, breastfeeding is usually considered safe as only a very small amount of the medicine enters your breast milk.

Should you make any dietary changes during pregnancy with Hashimoto’s disease?

A regular healthy diet is recommended. In addition, you should also make sure you eat a diet rich in iodine as this is important for helping the thyroid to make thyroid hormones. You can get iodine in foods such as seafood, eggs and iodized salt. You may wish to take a prenatal supplement.

Hypothyroidism is manageable during pregnancy and throughout the post-partum period.

International Pharmacy has provided this article for general information only and it does not replace medical advice. For support with diagnosing and treating hypothyroidism during pregnancy, make sure you consult your own healthcare team.