TABLE 1.

Physiological levels of progesterone in serum according to gender, menstrual cycle phase, and pregnancy status

Gender or stage	Range (ng/ml)a	Concn used in the study
Males	≤0.2	0.25 ng/ml (0.8 nM PRO)
Postmenopausal women	≤0.2
Follicular phase	≤0.89
Ovulation phase	≤12	2.5 ng/ml (8 nM PRO)
Luteal phase	1.8–24
First trimester	11–44	25 ng/ml (80 nM PRO)
Second trimester	25–83	50 ng/ml (160 nM PRO)
Third trimester	65–290	150 ng/ml (480 nM PRO)

^aClinical progesterone level in serum according to the Mayo Clinic (https://www.mayocliniclabs.com/test-catalog/Clinical+and+Interpretive/8141) and the University of Rochester (https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=167&ContentID=progesterone).