While giving sex education to school & college students we always showed them live motile sperms under a microscope. We were shocked once to see that a fresh semen sample from a young donor had no sperms at all.
India’s stastistics show that more and more  couples are not having babies. Already every 10th to 15th couple has no baby. Because of pollution and many other factors the infertility is increasing.
So to all  young people one must tell,”  welcome your first child today, for one may never come tomorrow.”