What supplements/dietary changes?
extra vitamin c (thought not too much) as I've been told it helps strengthen the amniotic sac. It seems to work as I've never once had my water break before it was time to push. And my midwife last time said it looked like "a huge water balloon, it's gotta pop soon!"
Calms Forte, not really for "optimal health" unless you count finally getting sleep optimal health. Which I do.
Red Raspberry Leaf tea starting at 30 weeks to help tone the uterus for the birth.
otherwise, just my usual diet, i work on getting extra healthy food as I was morbidly obese after having DD2, and have managed to lose 40 pounds... I don't want to go through that again.