Thyroid hormones are crucial for normal development of your baby’s brain and nervous system.
Untreated severe hypothyroidism during pregnancy can lead to:
- preeclampsia—a dangerous rise in blood pressure in late pregnancy
- low birthweight
- congestive heart failure, rarely
Levothyroxine is safe for your baby and especially important until your baby can make his or her own thyroid hormone.
If you had hypothyroidism before you became pregnant and are taking levothyroxine, you will probably need to increase your dose. Most thyroid specialists recommend taking two extra doses of thyroid medicine per week, starting right away. Contact your doctor as soon as you know you’re pregnant.
Your doctor will most likely test your thyroid hormone levels every 4 to 6 weeks for the first half of your pregnancy, and at least once after 30 weeks. You may need to adjust your dose a few times during the pregnancy.