no crash, they don't do that. in the first matrix morpheus clearly says human beings aren't born anymore. so they wouldn't be putting any man's sperm in any woman's uterus. they grow them. we saw that in the movie.
if i had to, i'd hypothesize that they just let the people in the matrix have their mating fun, and anytime they need a new kid they start growing one and let one of the women in the matrix be pregnant.
i wouldn't say it's a plot hole, cuz there's a number of ways it could go. it's just not important to the story, so they never tell us.