Look, my aunt is an OBG, and since my mom works with her I hear stories about pregnant women and their woes on a daily basis. I hear 50yo women coming in pregnant with their first kid when they should be on the brink of menopause and they deliver just fine.
All I can say is that every stage in a woman's life has their risks, and there isn't one specific age that would be best. Just, over twenty, under thirty-five. The worst thing you could be is paranoid.
But yeah, if I had to choose an age, 25-ish would be the best.