Previously, we have reported an association between low levels of intraovarian cortisol metabolism, mediated by 11β‐hydroxysteroid dehydrogenase (11βHSD), and the establishment of pregnancies by in vitro fertilization and embryo transfer (IVF‐ET). The objective of the present study was to investigate the relationship between the clinical outcome of IVF‐ET and the intraovarian concentrations of cortisol and cortisone and the cortisol:cortisone ratios in random samples of ovarian follicular fluid (FF).

Retrospective, double‐blind correlation analyses.

FF samples (n = 41) were obtained from 23 women undergoing gonadotrophin‐stimulated IVF‐ET cycles at the Cardiff Assisted Reproduction Unit.

Clinical pregnancy was confirmed by ultrasonography. Intrafollicular steroid concentrations were measured by radioimmunoassays.

Concentrations of both cortisol and cortisone were significantly lower in FF samples obtained from 6 patients that conceived than in samples obtained from 17 patients that did not achieve pregnancy (cortisol (mean ± SEM) = 304 ± 29 vs. 407 ± 26 nmol/l, P = 0.0411; cortisone = 32 ± 3 vs. 65 ± 7 nmol/l, P = 0.0002). Intrafollicular cortisol:cortisone ratios were significantly higher in samples from conception cycles than in those samples obtained from nonconception cycles (9.7 ± 0.7 vs. 6.9 ± 0.5, respectively, P = 0.0060). Whereas 5 of 10 women with intrafollicular cortisol:cortisone ratios greater than the outcome‐independent mean of 7.7 became pregnant, only 1 of the 13 patients with intrafollicular cortisol:cortisone ratios < 7.7 conceived (χ² = 5.247, P = 0.0220).

Concentrations of both cortisol and cortisone were significantly lower in FF samples obtained from patients that conceived by IVF‐ET than in those obtained from nonconception cycles. Conception by gonadotrophin‐stimulated IVF‐ET was associated with an elevated intrafollicular ratio of cortisol:cortisone, consistent with a low level of intraovarian cortisol oxidation by 11βHSD.