Here's a "top 10" from Mary Shomon's About.com thyroid guide:
Researchers, reporting in the January 2006 issue of the journal Pediatrics, have reported that there is an increased risk of neurological problems in infants when the mother was hypothyroid -- had low thyroid hormone levels -- early in the pregnancy, even if the mother had no symptoms...
...Some experts are now agreeing that routine screening of thyroid function in pregnant women during the early part of the first trimester may be warranted, given these current findings.
Obviously, they haven't mandated it yet, probably the insurance companies think it's too costly. I remember my primary care doc hemmed and hawed over getting me tested, and then my TSH came in at a 9 (fairly high!) with an extra helping of bad antibodies, and even then he wasn't too urgent about referring me to an endo even though he knew we were trying to get pregnant.
You have to take charge of your own health!
Read the whole article here.