 We plan to follow vitamin D in infertile women undergoing IVF treatment for various indications, at baseline, during and after controlled ovarian hyperstimulation. Their levels will be measured at baseline when they first present for basic investigations at our clinic, during the down-regulation phase of their treatment if their protocol has a down-regulation phase, at each follow-up visit during stimulation when they are asked to present for measurement of their estradiol E2 levels, as well as at the conclusion of their treatment i.e. the day of their pregnancy test. Along with endocrinology profiles, we will also record all the details of treatment outcomes in terms of embryo quality, implantation and clinical pregnancy rates. We also intend to perform follow-up studies of pregnancy outcomes. 