 Those patients who consent to participate in our study will have vitamin D levels drawn at each visit, but will not be required to present more often than otherwise required by their treating physician. Given that the only intervention is one additional blood sample, we do not foresee any side-effect or risks. Results of these tests will not have any impact on patients IVF treatment protocols, as the test results will not be disclosed until after their treatment has ended, whether in failure or in pregnancy. 