Hyperthyroidism and Graves' Disease During Pregnancy

Signs, Symptoms, and Risks

Hyperthyroidism can be serious during pregnancy. Credit: istockphoto.com / Getty Images

Hyperthyroidism -- an excess of thyroid hormone -- can occur during pregnancy. Because of potential risks to both mother and baby, it's a condition that needs to be taken seriously, and properly treated.

How Does Graves' Disease Affect a Pregnant Woman and Her Baby?

The autoimmune condition Graves' disease is the most common cause of hyperthyroidism during pregnancy. Hyperthyroidism due to Graves' disease in pregnancy is not common: It's estimated that some 1 in 500 women develop it during pregnancy.

It can be serious, however. Typically, this form of hyperthyroidism persists more than several weeks and beyond the first trimester. Graves' disease typically becomes less severe as the pregnancy progresses.

What are the Risks of Graves' Hyperthyroidism to Mother and Baby?

Uncontrolled or untreated hyperthyroidism, especially during the second half of pregnancy, can lead to a variety of serious consequences for both mother and baby. When hyperthyroidism is not properly treated during pregnancy, a pregnant woman is at higher risk of a number of complications, including heart problems, high blood pressure, extreme morning sickness, preeclampsia, congestive heart failure, and even a life-threatening condition known as thyroid storm, where heart rate and blood pressure become uncontrollably high. Thyroid storm can be triggered by labor and delivery in a woman with untreated hyperthyroidism.

The risk to the baby is also significant, as untreated hyperthyroidism in a mother can cause:

  • Miscarriage
  • Intrauterine growth retardation
  • Prematurity
  • Low birth weight
  • Stillbirth
  • Hyperthyroidism in the fetus or newborn

What Other Forms of Hyperthyroidism Can Occur During Pregnancy?

A hormone that develops during pregnancy -- human chorionic gonadotropin (hCG) -- rises soon after fertilization, peaks at 10 to 12 weeks of gestation, and then declines.

HCG can weakly stimulate the thyroid, resulting in a milder, shorter-term form of hyperthyroidism during pregnancy.

This transient subclinical hyperthyroidism is also known as gestational transient thyrotoxicosis -- sometimes abbreviated as GTT. GTT usually resolves during the first trimester of pregnancy, and usually does not involve treatment.

The rise of HCG is also linked to a condition known as transient hyperthyroidism of hyperemesis gravidarum, which involves hyperthyroidism, nausea, vomiting, and loss of 5% percent or more of body weight during early pregnancy.

What are the Signs and Symptoms of Hyperthyroidism in Pregnancy?

The symptoms of hyperthyroidism in pregnancy may be hard to identify, because they are similar to those of pregnancy itself. Fatigue, anxiety, insomnia -- all common symptoms of pregnancy -- are also symptoms of hyperthyroidism.

Neck enlargement (goiter) is seen in almost all pregnant women with Graves' disease and hyperthyroidism, as the gland usually is enlarge to two to four times its normal size.

Other symptoms of hyperthyroidism in pregnancy include:

  • Failure to gain weight during pregnancy, or weight loss, despite increased or normal appetite
  • Pulse rate over 100, known as "tachycardia"
  • Heart palpitations
  • Irregular heart rates (arrhythmias) including atrial fibrillation
  • Higher blood pressure
  • Difficulty concentrating
  • Excessive nausea and vomiting
  • Nervousness, anxiety, restlessness, fidgety behavior
  • Depression, moodiness
  • Tremor
  • Intolerance to heat, excessive sweating
  • Diarrhea
  • Arm and leg muscle pain or weakness
  • Difficulty climbing stairs
  • Vision problems: i.e., stare or protrusion of the eyes, blurred vision, double vision, etc. -- also known as ophthalmopathy
  • High heart rate in the baby, typically a heart rate of more than 160 beats per minute
  • Fatigue, exhaustion

Since women can experience a variety of symptoms during pregnancy, it may be difficult to identify hyperthyroidism symptoms compared to normal pregnancy symptoms.

Two key symptoms should be taken seriously, however: Both a rapid pulse and unexplained weight loss are not typical in pregnancy, and likely point to hyperthyroidism.


American College of Obstetricians and Gynecologists (ACOG). "Guideline: Thyroid disease in pregnancy." Washington (DC): 2002 Aug. 10 p. ACOG Practice Bulletin No. 37. Online

Braverman, MD, Lewis E., and Robert D. Utiger, MD. Werner and Ingbar's The Thyroid: A Fundamental and Clinical Text. 9th ed., Philadelphia: Lippincott Williams & Wilkins (LWW), 2005.

Ross, Douglas. "Causes and clinical manifestations of hyperthyroidism during pregnancy." UpToDate.  Accessed: February 2009.