Age-specific FSH levels as a tool for appropriate patient counselling in assisted reproduction.

Background: The purpose of this study was to assess whether, even within a normal FSH range (< or =10 mU/ml), age-specific FSH levels are predictive of ovarian reserve.
Methods: Between January 1998 and December 2001, 535 women, undergoing controlled ovarian stimulation with 225 IU of recombinant (rec) FSH and 75 IU of recLH, were included in this retrospective cohort study. Criteria for enrolment were: age 25-40 years, basal FSH (b-FSH) < or =10 mU/ml and basal LH < or =12 mU/ml. Patients were assigned to three age groups (group I: 25-29 years; group II: 30-35 years; and group III: 36-40 years). Each age group was divided into quartiles according to b-FSH levels, comparing the lowest and highest b-FSH quartiles for basal hormonal patterns and outcome-related parameters.
Results: At ages 25-35 years, women in the lowest FSH quartiles demonstrated significantly increased numbers of oocytes at retrieval (group I: low b-FSH quartile 8.4 +/- 3.7 versus high b-FSH quartile 6.4 +/- 2.7, P < 0.02; group II: 7.5 +/- 4.0 versus 6.3 +/- 3.0, P < 0.047), whereas no difference with regard to oocyte yield was observed in patients above age 35 (group III: low b-FSH quartile 5.5 +/- 3.1 versus high b-FSH quartile 5.6 +/- 3.5). No statistical correlation was found between FSH quartiles and clinical pregnancy rates or miscarriage.
Conclusions: In young women, age-specific high b-FSH levels, even within normal ranges, are associated with significantly reduced numbers of oocytes retrieved. B-FSH concentrations should, therefore, be interpreted in an age-specific manner to allow for appropriate patient counselling in IVF.