Hi T.:
My Mom and I both have Hashimoto's thyroiditis. (Auto immune disease where anitbodies attack the thyroid leading to hypothyroidism.)
She has been on synthroid for years without a problem. The only complication is adjusting the medication to get the correct dosage. Although, I will tell you that she has been told by several different endocrinologists to make sure that she takes the brand name drug synthroid NOT the generic. (She did not develop it after pregancy. More like 20 years later.)
As far as being on synthroid during pregnancy DO NOT WORRY. (And trust me, I am the kind of person who thinks that I can tough it out through a headache instead of taking the tylenol.) I am in my second trimester with my first child and I have had several endocrinologists recommend that I take synthroid through my pregnancy because the baby depends so much on the mother's thyroid for proper development. My OBG also told me that it is common for women to develop hypothyroidism after giving birth because your thyroid is really beat up during pregnancy because of the demands the growing baby puts on it. I will let you know that some women do become hypothyroid after pregnancy and then go back to normal after taking synthroid for a while.
Lastly, if you need recommendations for endocrinologists I have 1 at Rush who is great another at Northwestern. Just let me know aand I am more than happy to share with you.
Good luck!
A.