Fig. 2. (a) Progesterone and (b) estrogen blood concentrations (mean ± SE) of pregnant (P) and respective non-pregnant (NP) and negative control cycles (NC). Results of the SAS mixed model indicating significant (p < 0.05) differences regarding the fixed effects group, time and group × time are shown in the table. Different letters (a, b) indicate significant differences between P, NP, and NC.