Ovarian follicular volume and follicular surface area are better indicators of follicular growth and maturation, respectively, than is follicular diameter.

Because ovarian follicular growth occurs in three dimensions, and because follicular maturation (increased E(2)) is a result of an increase in the three-dimensional follicular surface area where testosterone (E(2) precursor)-producing theca interna cells are located, the three-dimensional follicular volume and the three-dimensional follicular surface area describe the three-dimensional follicular growth and maturation, respectively, more accurately than does the two-dimensional follicular diameter alone. Therefore, we present a mathematical model that describes the relationship of the two-dimensional follicular diameter, the three-dimensional follicular volume, and the three-dimensional follicular surface area to the three-dimensional follicular growth and maturation.