Women utilizing oocyte donation have a decreased live birth rate if they displayed a low progesterone level in a previous hormonal replacement mock cycle.

A low P level in hormonally substituted cycles several years before ET performed with the same endometrial preparation is associated with a significantly lower chance of live birth. This suggests that altered vaginal P absorption is a permanent phenomenon. Monitoring serum P in hormonally substituted cycles appears mandatory to adjust luteal P substitution.