Sterility and infertility are different concepts; to understand fertility, one of the key concepts to know is that, in general conditions, the human species has a low reproductive efficiency with only between 20 and 25% of monthly pregnancy possibility in fertile couples and without any problem, reaching 80% of accumulated pregnancy rate throughout a year of searching and 90% after 2 years of searching for gestation.
Sterility is defined as the inability of a couple to conceive naturally within one year. Within this term, a distinction can be made between primary sterility, if the couple has never become pregnant, and secondary sterility, if the couple has already achieved a pregnancy previously, but at the present time is unable to become pregnant.
Infertility, on the other hand, is understood as the inability to achieve a live birth, this being the case of couples who achieve pregnancy but subsequently miscarry.
Therefore, although sterility and infertility are often referred to interchangeably, they are different concepts, although they have in common the inability to achieve an evolving pregnancy and a newborn.