Saliva progesterone throughout the menstrual cycle and late pregnancy

Whole saliva was collected daily by four women during one menstrual cycle and twice weekly by three women during their third trimester of pregnancy. Follicular-phase saliva progesterone concentrations, as measured by radioimmunoassay, generally remained below 50 pg/mL. However, progesterone rose to a peak of 400 ± 107 pg/mL (mean ± SE) between days 17 and 25, after which it declined to 143 ± 67 pg/mL by one day prior to menses. The third trimester of pregnancy was characterized by steadily increasing concentrations of saliva progesterone until 1–3 weeks prior to parturition; concentrations following parturition were similar to those of the follicular phase.