Has anyone had any extra testing done for thyroid levels in their pregnancy?

My doctor has been keeping an eye on them, and I have to get re-tested even after testing normally the last time I got blood work. She didn't really explain to me why they were doing it, and I've tried researching but dont think any of it applies to me. My OB is very cut and dry, so she doesn't explain anything in depth if she doesn't feel the need too.