Background: A cycle day 3 FSH concentration is a popular screening tool for predicting success in achieving pregnancy after IVF. Difficulties interpreting this test have resulted from lack of consensus in defining an elevated FSH concentration, a change in the assays, and lack of controlling for factors which may confound the association between FSH concentration and pregnancy.
Methods: Assessment was made of the ability of a moderately elevated (10-11.4 mIU/ml, World Health Organization 2nd International Standard (IRP 78/549) and elevated FSH (>11.4 mIU/ml, conversion factor to SI units, 1.00) in predicting ability to achieve pregnancy through IVF and embryo transfer, both independently, and after controlling for confounding variables such as age, diagnosis, and response to gonadotrophins.
Results: A total of 293 IVF cycles were retrospectively reviewed. An FSH (>11.4) was strongly associated with inability to achieve pregnancy after IVF both independently (P < 0.01) and after multivariate analysis (P < 0.01), and had a strong predictive value (100%). A moderately elevated FSH (10-11.4) was not statistically associated with pregnancy outcome either independently or after multivariate analysis, and had a low predictive value (71%).
Conclusions: Much of the predictive value of an elevated FSH is confounded by poor response to gonadotrophin stimulation, which may be overcome in younger women.