Biological versus chronological ageing of oocytes, distinguishable by raised FSH levels in relation to the success of IVF treatment.

BACKGROUND: The present study addresses the issue of biological ageing of the oocyte (as indicated by basal serum FSH levels) versus chronological ageing. METHODS: 1019 infertile but ovulating women were studied in their first cycle of IVF treatment. A series of logistic regression models were developed to assess statistical significance of effects of age and FSH on implantation rates and live babies born. RESULTS: The number of oocytes retrieved and embryos available for transfer declined with increasing age and basal serum FSH concentrations. Fertilizing ability of oocytes increased with advancing age but was not affected by FSH concentrations. Although the number of oocytes or embryos available for transfer had no independent effect on implantation rates, the implanting ability of fertilized oocytes (embryos) was inversely related to increasing age and independently to FSH. The chance of a baby being born, however, was determined more by age than by serum FSH. CONCLUSIONS: Ovarian ageing affecting oocyte quality and fecundity can occur independently of chronological age. This has important practical implications whereby serum basal FSH measurement may be a valuable prognostic index, though chronological age remains important.