To determine whether alterations in preovulatory follicular fluid (FF) levels of LH, FSH, and steroids are associated with the probability of fertilization. Retrospective analysis of prospective study results. Reproductive medicine clinic of a university teaching hospital. Infertile women, with unstimulated, apparently regular cycles in an IVF research program. Measurement of preovulatory FF levels of LH, FSH, E2, and P and serum LH levels by fluoroimmunometry. Oocyte fertilization. There were 84 transferable embryos (rate of normal fertilization and cleavage, 67%), and 41 oocytes (33%) failed to fertilize. Analysis of the matched FF showed that the median concentration of FF LH was significantly higher for cleaving embryos than for unfertilized oocytes (14.6 vs. 10.4 IU/L). Serum LH concentrations were similarly higher in cycles with cleaving embryos. There were no statistically significant differences in FF concentrations of FSH, E2, or P in the two groups. Reduced preovulatory FF LH levels are associated with impaired fertilization of oocytes in vitro, despite normal FF FSH and steroid levels.
