Midluteal Progesterone/Estradiol Ratio as an Indicator of Pregnancy Potential

: In an effort to determine the reliability of the midluteal progesterone(P)/estradiol(E2) ratio as an index of the potential for conception, we measured the midluteal P and E2 levels in 76 infertile women who had been treated at our infertility clinic. This parameter in conception cycles was compared with that in non-conception cycles. Eighty cycles of the 76 women were classified into two groups, depending upon whether pregnancy occurred or not. Group 1 and group 2 were composed of 31 conception cycles and 49 drug-induced cycles, respectively. Midluteal concentrations of P and E2 did not show any significant differences between the two groups. The P/E2 ratios were 106.4 +/- 71.3 (mean +/- SD) and 71.5 +/- 44.16, respectively. This difference was statistically significant (p less than 0.05). Discriminant function analysis showed that the smallest probability of misclassification between the two groups decreased from 44% when using P only to 36% when using the combined P and E2. The following equation: Y = 0.0727X1 - 0.00456X2 - 0.130 was obtained (when X1 = P, X2 = E2). These results suggest that the midluteal P/E2 ratio gives clinicians the best indication of luteal function for the achievement of pregnancy.