Have you ever heard of the Brewer Diet for pregnancy? It was developed (decades ago, so not a fad, really) for low income women who were at higher risk for gestational diabetes. There is a lot of great science behind it. I believe for a time it was referred to as the Blue Ribbon Baby Diet.
I followed it loosely my first two pregnancies, following the protein guidelines but also eating way too much junk, then more seriously with my youngest (who is 20m and still nursing). She was only 7lbs 13oz, and I gained 30lbs with her, exactly like I did the first two, but instead of it taking me two years to take it off like before, in just two months I was within 5lbs of pre pregnancy without doing anything remotely resembling dieting.
I honestly believe, from my own experience, that the better we eat during pregnancy, the easier that weight comes off.
Congratulations on your pregnancy!