Figure 1.

Progesterone levels across the lifespan: [Inset A) across the menstrual cycle, B) across pregnancy].

Legend: Progesterone levels increase from <1 ng/mL before age 10 to 10–12 ng/mL around puberty. Throughout the reproductive years levels range from 3 to 35 ng/mL in the luteal phase, decreasing in the late luteal phase, and are <1 ng/mL in the follicular phase (Inset A). In postmenopausal women, progesterone levels wane to <0.2 ng/mL. In pregnant women (Inset B), progesterone levels increase from 10–35 ng/mL in the 1^st trimester to 100–300 ng/mL in the 3^rd trimester; progesterone levels then drop to low levels postnatally as prolactin levels increase to facilitate lactation and return to average reproductive age ranges when ovulation returns.