1. In the future a disease has wiped out much of the female half of the population. Because of this some are chosen for breeding. Evolution has looked kindly upon them and now the pain of childbirth is less than before and accompanied with an intense arousal that lasts the entire time. Another woman, an attendant, tends to and pleasures the woman through her labor.
2. In the distant future earth and mankind have been taken over by a race of aliens. Any men are kept for the sole purpose of breeding more humans because, and the reason for their take-over, the aliens can only reproduce through human females. Once impregnated one or two eggs grow to the size of a grapefruit. At this point the woman is given a serum that will induce labor and change her labor symptoms - instead of pain during her labor and contractions she will experience intense pleasure. Another human woman is there to pleasure and comfort her through the process.