Ongoing pregnancy rate, defined as positive fetal heart action 9 weeks after the first positive pregnancy test. Number/diameter of follicles, number of oocytes retrieved, number of pronuclear oocytes (referred to as zygotes or pre-embryos in the UK), quality of pronuclear stage oocytes, number of embryos transferred, quality of embryos, number of frozen embryos, endometrial thickness and morphology on day of HCG administration, estradiol levels at day of HCG administration, implantation rate, number of days stimulated with gonadotrophins and number of ampoules used, clinical pregnancy rate at 6 weeks after the first positive pregnancy test, pregnancy outcome.