My first labour started with PROM at 36 weeks.

When I got pregnant the second time I was worried about this happening again, did a bit of research and found that taking vitamin C throughout pregnancy can make the amniotic membrane a bit "tougher" (vitamin c is linked to collagen production and quality).

FWIW I did it, and the second time no issues with PROM at all and I got to 38 weeks. Obviously that's purely anecdotal but who knows, it might have helped. Perhaps it would help your membranes hang in there a bit longer when labour start as well.

There have actually been a few studies on it though, have a google.