Women's  Healthcare Topics is a website about pregnancy and your newborn baby.

Thyroid Disease in Pregnancy

Reviewed by James Brann, M.D.

Thyroid Disease can Complicate Pregnancy

Learn about how pregnancy will affect hypothyroidism.

About 20 million Americans have some form of thyroid disease. Though thyroid problems can affect anybody, women are five to eight times more likely than men to develop them. As with any pre-existing illness, thyroid disease can complicate pregnancy.

Your thyroid is a small, butterfly-shaped gland that rests in the middle of your lower neck, just above the collarbone. It is one of your endocrine glands, and its main function is to control your metabolism-which converts the food you eat into energy that your body can use.

Your metabolism tells you when you're feeling tired or well-rested, and whether you are hot or cold. To control metabolism, your thyroid gland produces and releases two hormones, T4 and T3, which control the rate at which every part of your body works. When your thyroid is working properly, your metabolism stays at a steady pace.

The thyroid gland is controlled by the pituitary gland, which is located at the base of your brain and produces the thyroid-stimulating hormone (TSH). TSH is carried through your bloodstream to the thyroid, where it tells the thyroid whether it needs to produce more thyroid hormones or not.

During the first trimester, your baby relies on your supply of thyroid hormone for his or her brain and nervous system development. Your baby's thyroid does not function on its own until week 10 or 12 of gestation. However, throughout the rest of your pregnancy, your baby continues to get his or her supply of iodine (which is produced by your thyroid) from the foods you eat. Because your thyroid function is so critical to your baby's health and development, thyroid problems must be controlled during pregnancy.

Thyroid disease occurs when your body produces too much or too little of the thyroid hormone. If your body does not make enough thyroid hormone, you have hypothyroidism (underactive thyroid) and this can cause your body's functions to slow down. On the other hand, too much of the hormone is called hyperthyroidism (overactive thyroid) and it can make your body's functions speed up.

During pregnancy, your pregnancy-related hormones, estrogen and human chorionic gonadotropin (hCG), causes an increase in your thyroid levels. This can often complicate pregnancy for women with hyperthyroidism. If the disease is not controlled during pregnancy, the pregnant mother can experience a thyroid storm, irregular heartbeat, and even heart failure. The baby is at an increased risk of smaller birth size, preterm birth, possible fetal death, and hyperthyroidism that requires treatment after birth.

If you have mild hyperthyroidism, in which your TSH is low but your T4 level is normal, you won't need treatment. Women with severe disease can be treated with certain medications that interfere with thyroid hormone production. Because these anti-thyroid drugs cross the placenta, it can decrease the baby's thyroid hormone production. Your doctor may prescribe you a lower dosage of medication. In rare cases, surgery to remove part or all of the thyroid gland may be an option.

In the case of hypothyroidism, these women face an increased risk of preterm birth and preeclampsia (a pregnancy complication characterized by high blood pressure) and placental abruption (your placenta starts to separate from your uterus before your baby is born). Your baby may be smaller in size and have decreased mental ability. Hypothyroidism is treated with synthetic thyroxine, which is identical to T4 and it is safe to use during pregnancy.

Pregnant women with thyroid problems should have their thyroid function checked every six to eight weeks.

In some cases, women with healthy thyroid function during pregnancy can develop problems postpartum. Postpartum thyroiditis, an inflammation of the thyroid gland, can occur within two to six months after you have your baby. Often, it is short lasting (symptoms last less than two months) and it is treated with beta blockers.

Unfortunately, in some women who have postpartum thyroiditis, their thyroid becomes too damaged and it is unable to regain normal function. They may need to take thyroid medication for the rest of their lives.

Postpartum thyroiditis shares similar symptoms as postpartum blues, such as exhaustion and moodiness. If your fatigue and lethargy do not go away within a few months, talk to your doctor.

Remember that changes to your thyroid function during pregnancy are normal, but they can sometimes lead to thyroid disease. Always talk to your doctor or healthcare provider if you have any concerns.

top

Pregnancy A to Z