Thinking Pregnancy? Think Thyroid Testing

by Baylor Scott & White Staff on September 25, 2012

in Pregnancy

Amanda’s mother Karen has hypothyroidism. Karen’s thyroid gland doesn’t make enough thyroid hormone, and she has to take daily thyroid medication.

Amanda is 28 years old and would like to have a baby. Amanda’s physician suggested she first have a thyroid function test.

“Women who are thinking about getting pregnant, especially if they have a strong family history of thyroid disease, should get a thyroid function test done before conception,” counsels Deepika Reddy, MD, Endocrinologist

“It’s better to fix the issue well ahead of time because most women don’t know they’re pregnant until well into their pregnancy — and fetal organ development happens fairly early in the pregnancy,” Dr. Reddy explains.

How Does Thyroid Disease Affect Pregnancy?

“Have your thyroid levels checked and any problems with that taken care of before you plan to conceive.”

Your thyroid gland is about the size and shape of a large butterfly. It’s under your Adam’s apple at the base of your neck, right below your voice box (larynx). Your thyroid gland makes the thyroid hormone, called thyroxine (T4).

Thyroxine is the accelerator for every action in your body. An increase in T4 — hyperthyroidism — creates an increase in metabolism, whereas a decrease in T4 — hypothyroidism — slows down your metabolism.

Thyroid disease affects pregnancy in two ways:

  • It can harm the development of the fetus, particularly the development of the brain and central nervous system.
  • It can harm the health of the mother.

The effects depend, generally, on whether you have hyperthyroidism or hypothyroidism.


The Developing Fetus

Hyperthyroidism is the overproduction of thyroid hormone. If it’s not effectively controlled during pregnancy, according to the National Institutes for Health, hyperthyroidism in a developing fetus can cause:

  • Low birth weight
  • Premature birth
  • Miscarriage

“With hyperthyroidism, there may be abnormalities with bony development, and they may be small for gestational age,” cautions Dr. Reddy.

The Newborn

According to the NIH, uncontrolled hyperthyroidism in the newborn can cause:

  • Rapid heart rate, potentially resulting in heart failure
  • Premature closing of the soft spot in the skull
  • Failure to thrive
  • Irritability
  • Enlarged thyroid, causing difficulty in breathing

The Pregnant Woman

Uncontrolled hyperthyroidism can cause special difficulties for the pregnant woman, too:

  • Unexplained weight loss
  • Severe nausea and vomiting
  • Rapid and irregular heart beat
  • Congestive heart failure
  • Preeclampsia
  • Thyroid storm

“You have to worry about thyroid disease and pregnancy and watch it a little more, too,” says Dr. Reddy.

For women with a family history of thyroid disease, “it’s really important to get things sorted out first and then proceed with pregnancy,” Dr. Reddy advises.


The Developing Fetus

Hypothyroidism is the underproduction of thyroid hormone. If it’s not effectively controlled during pregnancy, according to the NIH, hypothyroidism in a developing fetus can cause:

  • Low birth weight
  • Stillbirth
  • Miscarriage

Moreover, “unregulated hypothyroidism can harm the development of your baby’s brain and central nervous system,” says Dr. Reddy.

Your developing baby depends on your thyroid hormone, supplied through the placenta during the first trimester, until it begins making its own thyroid hormone.

The Pregnant Woman

Uncontrolled hypothyroidism may also have serious consequences on the mother as well:

  • Extreme fatigue
  • Mental status difficulties
  • Preeclampsia
  • Anemia

“Again, I stress, because both hyperthyroidism and hypothyroidism have abnormalities associated with them, if you have a family history of thyroid disease, have your thyroid levels checked and any problems with that taken care of before you plan to conceive,” advises Dr. Reddy.

What If You Do Have Thyroid Disease?

If your physician suspects you have thyroid disease, he or she will run a series of lab tests to determine your thyroid hormone levels.

Your obstetrician will work in collaboration with your endocrinologist, Dr. Reddy says, to maintain stabilized thyroid hormone levels and ensure the best outcome for both you and your baby.

In some cases, you may be referred to a maternal-fetal specialist for more specialized care.

What About Thyroid Disease After Pregnancy?

In some cases, otherwise healthy women will experience a rise in thyroid hormone levels after delivery, says Dr. Reddy. This condition is called postpartum thyroiditis.

Postpartum thyroiditis, usually a mild form of hyperthyroidism, generally lasts for several months after your baby is born. In some cases, it may last up to a year or it may be lifelong.

Having postpartum thyroiditis after one birth increases your risk of having thyroid disease after future deliveries.

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