Introduction Embryonic implantation is a dynamic process of paracrine interactions between the maternal compartment and the conceptus and involves a receptive endometrium and a developmentally competent blastocyst. The process of implantation of a fertilized egg in the human uterus is governed by two crucial factors: endometrial receptivity and synchronization between embryonic and endometrial development. In a natural cycle, both these factors are related directly to cyclic ovarian hormone production and the timely occurrence of ovulation. In assisted reproduction, however, the events of ovarian stimulation of the donor and the artificial preparation of the endometrium of the recipient are completely separate. Therefore, it becomes essential to suitably manipulate endometrial growth with sequential administration of estrogen and progesterone in order to make the endometrium receptive to implantation.1 Normal menstrual cycle The menstrual cycle is controlled by the endocrine system. Normally, the endometrium proliferates under increasing levels of estradiol. This is known as…
Introduction The luteal phase of the menstrual cycle extends from ovulation to menstruation. The luteal phase is called so because it involves the process of luteinization, in which a structural transformation takes place in the luteinized cells of the collapsed follicle in response to increased vascularization.1 During the luteal phase, the corpus luteum secretes progesterone, which, along with estrogen, prepares the endometrium for the implantation of the embryo.2 The luteal phase normally lasts for at least 12 to 14 days. A luteal phase of less than 10 days' duration will have difficulty producing an environment favorable for implantation. Thus, a luteal phase defect (LPD) can interfere with a woman's ability to conceive, and is an important cause of infertility.3 In LPD, there is either an insufficient production of progesterone during the luteal phase or the endometrium does not respond appropriately to the progesterone stimulation. The end result is that the…
