Comparison of salivary steroid profiles in naturally occurring conception and non-conception cycles

Oestradiol and progesterone profiles from naturally occurring conception and exposed non-conception cycles were compared to assess the impact of natural variation in concentrations of ovarian steroid hormones on female fecundity. In a prospective, longitudinal study, 24 women collected saliva samples twice daily and recorded intercourse for up to 1 year or until a pregnancy was clinically confirmed. Oestradiol and progesterone concentrations were measured by a salivary radioimmunoassay. Average mid-follicular oestradiol concentrations were significantly higher in conception than in non-conception cycles (12.6 +/- 1.7 versus 8.5 +/- 0.6 pmol/l, P < 0.01). A separate analysis, including only cycles from those women who contributed both conception and non-conception cycles, demonstrated an even more pronounced difference in mid-follicular oestradiol concentrations, not just for conception and non-conception cycles as groups (14.5 +/- 2.3 versus 6.5 +/- 0.7 pmol/l, P < 0.001), but also between the conception and average non-conception concentrations of individual women. Among these women, relative mid-follicular oestradiol concentration was highly correlated with the probability of successful conception. In addition, relative body weight was significantly positively correlated with mid-follicular oestradiol concentration. These findings indicate that variation in follicular development, reflected in variation in follicular oestradiol concentrations, is an important indicator of fecundity.