Childfree Health

I recently heard a story from an intelligent and trusted friend about a woman who had major thyroid problems and was very overweight because of it who lost a bunch of weight (50+ pounds without even trying) while she was pregnant because the baby's thyroid gland functioned for her. (She gained it all back after the kid was born, of course.) I told my sister about this. She was recently diagnosed with thyroid disease, as was I (goiter and nodules and underactive.) My sister lost a bunch of weight (about 25 pounds) when she was pregnant too (7 years ago.)

I am d@mn sure not planning on having babies to "fix" my thyroid problem. My sister, who already has a kid, well I hope she's not planning that either, jeez, I hope not. (She told me herself she's not ready.)

(I can't help but wonder, too, if the kid's thyroid will give out on it at some point in it's life due to having the strain of functioning for both itself and mom before birth - this brings up questions of nature vs. nurture which are beyond the scope of my question, for sure.)

Just wondering if anyone had any info on this phenomenon. Is this a documented scientific fact?