Normal and Abnormal Thyroid Changes During Pregnancy: Origins, Outcomes, and Treatment Options

The nine months that it takes for a human infant to fully develop represent a period of tumultuous physical change for mother and baby alike. Even for women who experience a normal, healthy pregnancy, the sheer scope of the physical transformation that is part of the process can be difficult to cope with. But for some expectant mothers, the hormonal turmoil brought on by pregnancy can actually serve to worsen emergent or existing health problems.

Hormones function as the engine that drive the physical changes and growth processes of pregnancy. In order to fuel the rapid growth of the fetus and initiate the changes in the mother’s body that will allow her to sustain the growing baby and prepare for the challenge of labor and delivery, the body’s production of a number of different types of hormones spikes significantly during pregnancy.

The thyroid is also part of the body’s network of hormone-producing glands that is known as the endocrine system. The delicately-calibrated thyroid gland is designed to respond to even minute shifts in hormone levels. As a result, the massive influx of hormones caused by pregnancy can sometimes cause variations in thyroid function during this time in a woman’s reproductive life. In some cases, a developing pregnancy can foster thyroid dysfunction in expectant mothers.

Normal Changes in Thyroid Function During Pregnancy

Because of the hormonal changes that are an inevitable part of pregnancy, it is common for thyroid function to be impacted in expectant mothers. However, for the majority of women, these changes are not severe enough to cause any noticeable health problems or pregnancy complications.

One of the most commonly cited thyroid changes during pregnancy is a slight enlargement or inflammation of the gland that mimics some of the symptoms of a goiter, which is caused by iodine deficiency. However, in developed nations, most balanced diets offer ready access to iodine, and as such, true pregnancy-related goiters are very rare. In the vast majority of pregnant women, the outcome of this inflammation is a slight, temporary enlargement of the thyroid that is usually undetectable to the naked eye.

Pregnancy-Related Hypothyroidism

A thyroid gland that does not function at the proper rate causes hypothyroidism, which is the medical term for a deficit of thyroid hormones in the body. In some cases, expectant women are diagnosed with a new case of hypothyroidism during pregnancy; in other instances, the high thyroid hormone demands of pregnancy can worsen an existing, diagnosed, or marginal case of hypothyroidism.

If a pregnant woman’s hypothyroidism goes untreated, it can have a dire impact upon the health and development of the fetus. The thyroid hormone is largely responsible for propelling neurological and physical growth, and if maternal levels of the hormone are insufficient, especially during the first trimester, the infant may suffer cognitive and physical problems as a result.

However, if the disorder is diagnosed before or during pregnancy, it can be easily remedied with a drug regimen of replacement hormones. These compounds are safe to take during pregnancy, and the dose can be adjusted to best fit the needs of each patient.

Pregnancy-Related Hyperthyroidism

Much more common -- and more serious -- is the threat of hyperthyroidism during pregnancy. This disorder prompts the thyroid gland to function at a heightened pace, producing an excess of thyroid hormone in the system that essentially speeds up many of the bodily processes. In pregnant women, it can also cause early labor, pre-eclampsia, as well as being linked to an array of birth defects in developing fetuses.

By far the most common cause of hyperthyroidism in pregnant women is Grave’s disease, which effects as many as 1 in every 1500 expectant mothers. Women who have elevated levels of the hCG hormone, which is often linked to severe morning sickness, may experience episodes of hyperthyroidism. Also, existing cases of hyperthyroidism may be worsened by pregnancy hormones, causing them to be diagnosed for the first time, although they may have existed undetected for years prior to the pregnancy.

Compared to hypothyroidism, the diagnosis and treatment of hyperthyroidism in pregnant women can be somewhat difficult. Based on the severity of the case and the patient’s medical history, doctors usually devise personalized treatment plans that fit the needs of each expectant mother. In milder cases, monitoring the situation with frequent tests may prove to be sufficient. Drug treatment may be indicated in doses small enough to avoid harm to the fetus. In severe cases, surgical removal of the thyroid may be necessary.

Starting a Family? Be Mindful of Thyroid Health Issues

If you have a past history of thyroid problems, or if relatives have been diagnosed with thyroid disease, these issues should factor into the family planning process. Experts say it is best for women to have their thyroid conditions diagnosed and well-treated before becoming pregnant to ensure the best possible outcome for the baby. Whether you are pregnant now or are just beginning to consider parenthood, you can talk to your doctor about the possibility that pregnancy-related thyroid issues may pose a problem for you.