How does thyroid disease affect pregnancy?

Pregnancy-related hormones raise the level of thyroid hormones in the blood. Thyroid hormones are necessary for the baby's brain development while in the womb.

It can be harder to diagnose thyroid problems during pregnancy because of the change in hormone levels that normally happen during pregnancy. But it is especially important to check for problems before getting pregnant and during pregnancy. Uncontrolled hyperthyroidism and hypothyroidism can cause problems for both mother and baby.

Hyperthyroidism that is not treated with medicine during pregnancy can cause:

• Premature birth (birth of the baby before 39 to 40 weeks, or full-term)
• Preeclampsia, a serious condition starting after 20 weeks of pregnancy. Preeclampsia causes high blood pressure and problems with the kidneys and other organs. The only cure for preeclampsia is childbirth.
• Thyroid storm (sudden, severe worsening of symptoms)
• Fast heart rate in the newborn, which can lead to heart failure, poor weight gain, or an enlarged thyroid that can make it hard to breathe
• Low birth weight (smaller than 5 pounds)
• Miscarriage

Hypothyroidism that is not treated with medicine during pregnancy can cause:

• Anemia (lower than normal number of healthy red blood cells)
• Preeclampsia
• Low birth weight (smaller than 5 pounds)
• Miscarriage
• Stillbirth
• Problems with the baby's growth and brain development