Impact of ovarian hyperstimulation on the luteal phase

The contemporary approach to ovarian stimulation in IVF treatment results i n supraphysiological concentrations of progesterone and oestrogen in the lu teal phase. These sex steroids act directly and indirectly to mature the en dometrium, thus influencing its receptivity to implantation. The developmen t of endometrial receptivity is a complex process that may be altered by in appropriate exposure to sex steroids. Alterations in the oestrogen to proge sterone ratio, growth factor concentrations and cell adhesion molecule prof iles may occur after ovarian stimulation, potentially affecting the recepti vity of the endometrium. Recent clinical IVF studies have shown that implan tation rates and corpus luteum function are influenced by oestrogen concent rations during the early luteal phase. Few comparative studies have been pe rformed, but after ovarian stimulation there is a reduced implantation rate and a higher pregnancy loss rate before pregnancies can be detected clinic ally compared with natural cycle conceptions. Novel approaches to ovarian s timulation aimed at achieving a more physiological luteal phase endocrinolo gy are now being developed. Data from a recent pilot study by our laborator y, involving minimal ovarian hyperstimulation and no luteal phase support, are discussed.