Thyroid dysfunction and pregnancy

The type of symptoms you have depend on if your thyroid gland is too active, or not active enough.

Hypothyroidism

Symptoms of an underactive thyroid include:

• fatigue
• feeling cold easily
• hair loss
• constipation
• weight gain

Some people may not notice any symptoms.

Hyperthyroidism

Symptoms of an overactive thyroid include:

• weight loss
• sweating easily and feeling hot
• heart palpitations
• anxiety
• tremor (shaking)
• difficulty sleeping

Hypothyroidism

An underactive thyroid can be due to:

• not having enough iodine in your body
• an autoimmune condition called Hashimoto's thyroiditis
• previous damage to the thyroid gland

Hyperthyroidism

An overactive thyroid can be due to:

• an autoimmune condition called Graves' disease
• thyroid nodules
• a temporary effect of pregnancy hormones

If you are pregnant and have symptoms of thyroid problems, see your doctor and discuss your concerns.

If you know you have a thyroid condition, it's a good idea to see your doctor to check your thyroid while planning your pregnancy and again once you are pregnant. Your doctor will tell you how often you need a check-up.

Your doctor can diagnose hypothyroidism and hyperthyroidism with a blood test.

Your doctor will refer you for a blood test if you're pregnant and have:

• symptoms of thyroid dysfunction
• a known thyroid condition
• type 1 diabetes

They might also refer you for a blood test to check your thyroid if you:

• have a history of miscarriage or premature birth
• have a history of infertility
• are over 30 years of age
• have a family history of thyroid problems

If you have a thyroid problem, you should have blood tests regularly throughout pregnancy to make sure your thyroid hormone level stays in the recommended range.

If you have hypothyroidism, your doctor may prescribe a medicine called thyroxine. If you were already taking thyroxine before pregnancy, you may need to increase your dose when you become pregnant. Ask your doctor how much to take.

If you have hyperthyroidism, your doctor or specialist may prescribe an anti-thyroid medicine, such as propylthiouracil or carbimazole. If your thyroid is temporarily overactive because of pregnancy hormones, no treatment is usually needed.

Hypothyroidism

Low levels of thyroid hormone can cause complications such as:

• premature birth
• low birth weight
• miscarriage
• placental abruption
• pre-eclampsia

It may also affect your baby's brain development.

If your hypothyroidism is treated effectively, it will not cause problems for you or your baby.

Hyperthyroidism

If your thyroid gland is overactive during pregnancy, it may cause complications such as:

• miscarriage or stillbirth
• low birth weight
• preterm labour
• pre-eclampsia

Your baby may have a higher risk of developing hyperthyroidism. You and your baby may also have a higher risk of heart problems.

Not having enough iodine in your body can cause low thyroid hormone levels. During pregnancy, your body needs more iodine than usual.

Australian guidelines recommend that if you are pregnant, breastfeeding or planning to become pregnant, you should take a supplement containing 150 micrograms of iodine each day. This can be found in many pregnancy multivitamin supplements.

Ask your pharmacist if any of your prescription or over-the-counter medicines could affect your iodine levels and thyroid function.

Will my thyroid function return to normal after the baby is born?

If you have hypothyroidism, you will usually be able to return to your pre-pregnancy thyroxine dose after the birth of your baby.

After birth, about 1 in 25 people develop a thyroid problem called postpartum thyroiditis. This is when your thyroid becomes overactive for a short period, then becomes underactive, and finally returns to normal, within a year after the birth.

Read more about foods high in iodine.

Visit the Australian Thyroid Foundation for information and support.

Aboriginal and/or Torres Strait Islander peoples

Find an Aboriginal Community Controlled Health Organisation (ACCHO) in your area.