 Patients medical history, results of blood tests and the details of their IVF treatment protocol will be entered into a database, which will then be analyzed using parametric or non-parametric tests when appropriate, as required using SPSS. All blood tests levels will be drawn and analyzed in the McGill Reproductive Centers laboratory using a single immunoassay run. Measuring all samples at the same time reduces the possibility of inter-assay variability, reducing the sensitivity of the study. The sample size of experimental patients with 10 margins of error and 95 confidence limits is 66 women for a control group of 200. These numbers are easily achievable with the current activity of the McGill Reproductive Centre. 