In both men and women, in order for the reproductive system to operate correctly, the hypothalamus produces the primary hormone GnRH (gonadotropin-releasing hormone). That GnRH is then responsible for stimulating the production of LH (luteinizing hormone) and FSH (follicle stimulating hormone). In men, LH and FSH manage production of testosterone which is in turn responsible for production of semen, whereas in women those same two precursor hormones (LH and FSH) provoke production of estrogen and progesterone.
A woman is born with all of the eggs she will ever have (typically between 200,000 and 400,000) in her ovaries, in an immature form. The monthly menstrual cycle manages the maturity and release of one of those eggs. First, FSH causes a number of the immature eggs within a woman’s ovaries to grow into large follicles. Then a “surge” in LH causes ovulation — the release of the largest egg from the ovary into the fallopian tube to await potential fertilization. That LH surge also causes estrogen and progesterone to prepare the uterus with a rich lining in preparation for implantation of the fertilized egg. When fertilization does not happen, this lining (and the egg) leaves the woman’s body in the form of her menstrual period.
When a man ejaculates, his semen includes between 100 to 300 million sperm. Only 40 of these survive to reach past the cervix. In a typical pregnancy a single sperm then reaches and fertilizes the egg in the woman’s ovary, and that fertilized egg implants as an embryo in the uterine lining. Fertilization will only occur if the couple has sexual activity very near the time of ovulation. Sperm can live within the woman for up to six days, and most pregnancies occur within the two days prior to, or on the day of, ovulation.
If any of the steps outlined above fails — if either the man or the woman does not produce the correct or an adequate amount of hormones, if there are too few sperm or sperm that are not strong enough to reach and penetrate the egg, if the path along which either the egg or the sperm must travel is obstructed — then no pregnancy can take place. The complexity of the human reproduction process can make it difficult to isolate and determine the cause of infertility in every couple that has trouble getting pregnant. In fact, close to 30% of all infertile couples never receive a precise diagnosis and are instead deemed to have “unexplained infertility.”
Anna Short has developed expertise on infertility through a combination of personal experience and thorough research. For more great information on infertility, visit www.infertility-options-info.com. Be sure to sign up for her free email course on infertility.
