Diagnosing Infertility
Biology Basics
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Understanding your menstrual cycle is a critical step in getting pregnant. In order to achieve pregnancy, ovulation (release of the egg from the ovary) must occur. Therefore, one of the main questions women ask is, “How do I know I am ovulating?” The answer to this is fairly simple-- in general, women who have regular menstrual cycles can be fairly certain that they are ovulating. We know this because in order for a period to come regularly there are certain events that must occur in the ovary and uterus.
First, several of the immature eggs present in the ovary at the beginning of the cycle will begin developing and growing. The older a woman is, the less eggs are available every month. During the first 9 or 10 days of the cycle, one of the eggs is selected by the ovary to be the "dominant" egg that will eventually mature completely and be released. While it is maturing, the ovary produces estrogen which tells the brain that the ovary is working and also causes thickening of the uterine lining getting ready for implantation of a fertilized egg. Once this egg reaches maturity within its follicle (fluid filled cavity), a surge of hormones from the brain called LH (luteinizing hormone which can be measured by an ovulation predictor kit) causes release of the egg from its follicle. Once the egg is released, the now empty follicle is called a corpus luteum cyst and has the sole purpose of producing the hormone progesterone which acts as the glue keeping the uterine lining intact in preparation for an embryo implanting. The egg will then be picked up by one of the fallopian tubes and hopefully become fertilized by sperm in the tube and then travel into the uterus where it will implant into the thickened uterine wall.
If the egg is successfully fertilized by a sperm and does successfully implant into the wall, the tissue releases human chorionic gonadotropin HCG hormone (the hormone of pregnancy) which causes pregnancy tests to turn positive. If pregnancy does not occur, then the corpus luteum in the ovary stops producing progesterone after approximately 14 days and the lack of progesterone in the uterus causes the lining of the uterus to shed – the beginning of a woman’s period.