do you know what your results were?
Overly low T4 in pregnancy can affect fetal development. Very high TSH can affect their thyroid development, but only from aruond 2nd trimester as their thyroid hasn't formed before that.
In my first pregnancy I had ery low T4 at the start due to high estrogen levels after hyperstimulating (I had my thyroid removed a few years back and am on complete replacement) and high TSH, but DS developed fine anyway.
This pregnancy I've only just, at aournd 16 weeks, had to increase my dose. It may be that you didn't need any extra until this ponit anyway, in which case nothing untoward could have happened. If you're doctor was not worried, and your levels were normal for non-pregnancy, then I would suspect you're only just outside normal anyway, so it's probably nothing to worry about.