There are many causes of infertility including infertility of unknown causes, poor endometrial development, and diseases of the uterus. Other infertility causes such as endometriosis, ovulatory and tubal factor are discussed on additional pages.
The endometrium (lining of the uterus) must thicken and become more vascular during the menstrual cycle to support an implanting/developing embryo. Endometrial thickening is supported by the hormones estrogen and progesterone.
The corpus luteum is the structure in the ovary remaining after ovulation, and it produces estrogen and progesterone to support the endometrium. Once the placenta is formed, it begins to produce progesterone.
After virtually all IVF cycles, where normal progesterone production is inhibited by the drugs used to control ovulation (Lupron, Ganirelix, Cetrotide), progesterone is administered.
Infertility can be caused by “unknown factors.” A “diagnosis” of unexplained infertility is perhaps the most frustrating because a cause for a couple's infertility cannot be identified using standard tests. There is an “infertility cause(s)”; however, science has not progressed to the point where the specific defect can be identified. As research progresses, and new infertility causes are identified, the percentage of “unexplained infertility” cases should decline.
Many believe that unexplained infertility may be related to aspects of egg and sperm function/quality. The eggs may not fertilize without assistance or the sperm may not be capable of initiating “quality” fertilization.
A “first choice” fertility treatment for unexplained infertility may be IUI considering many other factors such as female age, previous treatments, etc. IVF may also be the treatment of choice especially after failed IUI cycles, if the female has declining ovarian reserve, or significant male factor infertility is present.
One advantage of IVF is that it allows the embryologist to view and document fertilization and the first stages of embryonic development. In this sense, IVF is both a diagnostic procedure looking for infertility causes, as well as a treatment.