Hi,
Hypothyroidism is more likely to cause fertility problems and if levels are too low developmental abnormalities can occur.
PTU has been safely used in pregnancy for more than 60 years. It only takes 6-8 weeks on PTU before patients move into a low maintenance dose. Doses below 200 mg daily are considered safe in pregnancy, and most people on maintenance doses are on doses of 100 mg or less.
Graves' disease is a self-limiting condition that usually improves and sometimes resolves during pregnancy. Most people during pregnancy are able to reduce their PTU dose or stop meds completely because the immune system slows down naturally in pregnancy.
Since Graves' disease is a self-limiting condition that typically resolves within a few years, patients aren't on meds very long compared to lifelong hypothyroidism, which isn't necessarily easy to regulate and requires lifelong replacement hormone. Best, Elaine