The number of children conceived by assisted reproductive technology is increasing in Nordic countries as well as worldwide. An important factor of success in treatment of infertility is a short "time to pregnancy" with impact on both economical aspects for the society and medical and psychological aspects for the couple. During treatment, success relies on 1) optimal stimulation of growth and maturation of multiple follicles by administration of exogenous follicle stimulating hormone (FSH), and 2) selection of the fertilized egg / embryo with the highest potential of implantation to be transferred to the mother. In the present project stimulation of egg production by human urine derived FSH (Fostimon®) and recombinant FSH (Puregon®) will be compared. To this end early embryo development and kinetics after fertilization will be evaluated. The system to be used is time-lapse recording of embryo morphology during the first days of embryo development by means of an embryoscope. Aim of this study is to investigate if Puregon and urinary Fostimon have different effect on embryo quality. The hypothesis of the study is that stimulation of egg production by these two types of follicle stimulating hormone does not have the same effect on early embryo quality.