What is the difference between fertility requirements and fertility potential?

The three basic elements – ovulation, tubes and sperm – outlined in the section above are required for falling pregnant naturally. However, the chance of being able to have a successful pregnancy (or fertility potential) is not guaranteed by merely having these three elements in place. Pregnancy success is also heavily dependent upon the egg being of very good quality. This is because egg quality is the rate-limiting factor for determining the potential of the early pregnancy (or embryo).