Oh, Catherine, I really hope it's not too late for your sister. Make sure to tell her to demand an u/s to make sure her baby is continuing to grow. That will make her feel much better.
Please keep me updated!
Here's the link the the thread. Just clink on an article to read. There is a ton of info for you and your sister.
Thyroid Information
Ahh, a knot is a different story. How tradgic, there isn't anything you could have done to prevented that, nothing.
Let me know if you have any other questions, Sweetie!