Progesterone-to-follicle index is better correlated with in vitro fertilization cycle outcome than blood progesterone level

Abstract

To investigate the impact of late follicular phase progesterone (P) elevation in relation to ovarian response on cycle outcome. Cohort study. The progesterone-to-follicle index (PFI) was calculated by dividing the blood P by the number of follicles ≥14 mm. The clinical pregnancy rate was calculated against the range of PFI values and blood P levels. In vitro fertilization unit. A heterogenous population undergoing IVF with pituitary suppression and gonadotropin stimulation resulting in 3-15 follicles ≥14 mm and blood P≤10 nmol/L on hCG day and resulting in fresh embryo transfer. None. Association of blood P and PFI with clinical pregnancy rate. Data were retrieved for 8,649 IVF cycles in normal responders. The (reverse) odd ratios for pregnancy were 1.112 (95% confidence interval [CI], 1.077-1.165) for blood P and 4.104 (95% CI, 3.188-5.284) for the PFI. Elevated P levels were associated with a lower pregnancy rate only when they reached the >93rd percentile. The PFI was inversely and linearly related to the pregnancy rate for the whole range of values. A late increase in P level is detrimental if it is a consequence of increased P production per follicle (high PFI) but not if it is a consequence of additional follicular recruitment. The PFI enables clinicians to differentiate these conditions.