Salivary Progesterone as a Biomarker in Pregnancy

Progesterone is considered as the pregnancy hormone. Already in 1958 Short was able to determine progesterone in blood and found that during pregnancy its levels increase from <0.1 μg/100 mL (nonpregnant) up to 87 μg/100 ml. In addition, Eton and Short found that in early abortion or premature delivery the concentration of progesterone was relatively low, which finding were confirmed by Wiest for fetal death. The role of progesteroneduring pregnancy includes the preparation of the uterus for implantation, to keep the uterus quiescent during gestation and lower immune responses of the mother. Initially, it is produced by the corpus luteum and after about 8 weeks by the placenta. It is suggested that a decline in progesterone levels facilitate the onset of labor and triggers milk production. Premature labour is characterized by progesterone concentrations lower than normal and may be prevented by the administration of progesterone, 17OHprogesterone or 17-hydroxyprogesterone-caproate. An update of this subject was given in a lecture during 14th Annual Symposium at the University of Illinois, Chicago, by Grobman, October 31, 2014.

The drop in progesterone levels as a trigger to the onset of labor has been assessed in sheep and other mammals and called‘P-withdrawal’. Attempts to confirm this mechanism in humans has been hampered by the fact that repeated blood sampling is too stressful and not feasible in situations that there is no health threat or medical indication.