Normative study of age variation in salivary progesterone profiles.

Daily luteal progesterone levels were measured for 124 regularly menstruating women, aged 18-44, by radioimmunoassay of steroid levels in saliva. A consistent pattern of age variation in luteal function was found, with the lowest levels of progesterone in the 18-19-year-old and 40-44-year-old groups, the highest values in the 25-34 year olds, and intermediate values in the 20-24 and 35-39-year-old groups. The striking similarity of this pattern of age variation with empirically and theoretically generated curves of apparent fecundability, suggests that age-related changes in ovarian function may underlie observed age variation in fecundability.