Hi. Can anyone give me any information on how an underactive thyroid can affect pregnancy? I had my thyroxine increased 6 weeks ago (i felt awful to the point I couldn't function and in a lot of pain)) Although I feel a bit better i'm having a blood test for pregnancy as my body is still playing havoc with symptoms! I'd be 6 weeks if I am. Not getting my hopes up but i'm hoping I am as had lots of problems in the past and was told (by a gp) it could be due to my thyroid and also thyroid problems can affect the baby as well if not controlled but not sure whether this is true or not.