Graves disease usually gets worse in the first half of pregnancy. It gets better in the second half, and then gets worse again after delivery.
It is important to keep your thyroid levels normal. Hyperthyroidism that is out of control may lead to preterm birth. This is birth before 37 weeks of pregnancy. It can also lead to low birth weight of the baby. The most common complication is preeclampsia. This is a kind of high blood pressure of pregnancy.
Some pregnant women have a severe life-threatening form of hyperthyroidism called thyroid storm. This is a condition in which there are very high levels of thyroid hormone. It can cause high fever, dehydration, diarrhea, fast and irregular heartbeat, shock, and even death, if not treated.
Medicines to treat hyperthyroidism may harm your developing baby and newborn. Birth defects are more likely with some anti-thyroid medicines. Anti-thyroid medicine may also cause low levels of thyroid (hypothyroidism) in the developing baby and newborn. A condition called neonatal hyperthyroidism may happen in a few newborns. It is usually short-term and does not cause problems for the baby, but careful monitoring is important.