Fecundity and fertility.
These are two similar concepts.
Fecundity is the biological capacity of an organism to conceive a child - in conjunction with another organism. For this to occur it is necessary that the man and the woman be fertile, that is, they have fertility. A person's fertility is measured by the number of ovules / seeds that can be fertilized. After fertilization, the fetus grows in the gestational process and becomes a baby.