Thyroid medication during pregnancy requires careful dose adjustments and regular TSH monitoring to protect fetal brain development. Levothyroxine is safe and essential-most women need a 20-30% increase right after conception.
Thyroid Medication During Pregnancy: What You Need to Know
When you're pregnant and taking thyroid medication, a synthetic hormone used to treat underactive thyroid, commonly prescribed as levothyroxine. Also known as thyroid hormone replacement, it's not just a pill you take—it's a key part of keeping your baby's brain and nervous system developing properly. Your thyroid works harder during pregnancy, and if it can't keep up, your body might not make enough hormone for both you and your growing baby. That’s why many women need to adjust their dose, often within the first few weeks.
Hypothyroidism in pregnancy, a condition where the thyroid doesn’t produce enough hormone, can increase the risk of miscarriage, preterm birth, and developmental delays if left untreated. But the good news? Levothyroxine, the most common thyroid medication used during pregnancy. Also known as Synthroid or Tirosint, it’s safe, well-studied, and doesn’t cross the placenta in harmful amounts. Doctors don’t just guess at the right dose—they test your TSH levels every 4 to 6 weeks, especially in the first half of pregnancy, because your body’s need for thyroid hormone can jump by 30% to 50%. You won’t need to stop it. In fact, stopping it can be more dangerous than staying on it. Many women start or increase their dose as soon as they find out they’re pregnant, and their doctors monitor them closely through blood tests.
Some women worry about side effects or long-term impacts on their child. But studies tracking thousands of pregnancies show no increased risk of birth defects or cognitive issues when thyroid levels are kept in the right range. What matters most is consistency—taking your pill at the same time every day, away from calcium, iron, or prenatal vitamins, which can block absorption. If you forget a dose, don’t double up. Just take it when you remember, or skip it if it’s almost time for the next one. Your doctor will help you adjust as your body changes.
There’s also a group of women who had thyroid issues before pregnancy and are now wondering if they’ll need to stay on medication after delivery. For some, yes. For others, the dose may go back down. That’s why follow-up testing after birth is just as important as it was during pregnancy. Thyroid function doesn’t reset just because the baby is out.
Below, you’ll find real-world insights from women who’ve navigated this journey, what doctors recommend when things get complicated, and how to spot signs your dose might need tweaking—without waiting for your next appointment.
