In my playthrough, it's relatively easy. I let male mc rape native girls, either when they're sleeping in bed or after wrestling( pressing R key) with them. In some cases, girls get impregnated when I use rape as a way to incapacitate and capture them. It seems that this game really rewards bad behaviorscant seem to get anyone pregnant, 40 tries and no dice
friend has the steam version and he can get some pregnant, neither of us have seen anything regarding a pregnancy bar however