I drove all through all 3 of my pregnancies........I was still driving when very overdue with Olivia, and my legs are short and my belly was big, but it still didn't hinder my driving.........

Where did your mother get her info from? Could it be just a dated "old wives tale" that she is repeating do you think?

If you have any pregnancy books, maybe check the index and fluro the bit that says that driving is totally OK, for your DH to read?