Nature has its way. Should a healthy, potent man mount a young woman and close to his orgasm he would be told that his mount was in her ovulation period the chances are high that he wouldn't stop ramming and instantly unload his semen and realise his instinctive urge to inseminate. Very natural.
It would surprise most people how many couples who want a baby cannot afford artificial insemination. Many of them seek a sperm donor for a natural insemination. Via donations at a clinic, my sperm has been identified as healthy, vigorous, and plentiful. Through referrals by clinic personnel, I have inseminated 8 wives.