Increasing levels of serum FSH in the early follicular phase, a characteristic of reproductive aging is often used to identify women who are likely to have a poor outcome with assisted reproduction. Counseling patients regarding the value of such a test appears on the surface to be fairly straightforward. However, immunoassays of FSH are intrinsically imprecise in certain ranges so that the comparison of results between different assay systems may be extremely difficult. This is important because there are substantial differences between the various commercially developed assays to measure FSH; differences in basal FSH determinations may be due to use of different FSH assays.
A part of infertility practice is directed towards identifying patients with a very poor prognosis and advising patients on their reproductive potential based on available testing. However, only a small group of patients will be labeled in such a way. The basal FSH serum test remains an important test for providers to determine the ovarian reserve and ovarian responsiveness prior to treatment. The test is useful for helping to determine the appropriate treatment protocol for individual patients.
Data clearly demonstrate a significant impact of both age and basal FSH levels with delivery rates in patients attempting conception through IVF. These data also demonstrate that there are basal FSH levels above which delivery is very unlikely but not impossible. However, the FSH values must be interpreted cautiously as even very elevated values do not always prognosticate failure in an IVF attempt.