Answer:
Infertility may be called unexplained only after the standard evaluation yields no
obvious cause. The three major factors causing infertility are: 1. sperm abnormalities;
2. disorders of ovulation; 3. anatomic factors such as tubal disease. Thus the standard
evaluation includes semen analysis, serum progesterone and tests of ovarian reserve,
and an HSG x-ray(hysterosalpingogram).
If these tests are all normal, then one could pursue less common causes of infertility, such as endometriosis, but the current approach is to focus on treatment rather than research of esoteric factors. The entry level treatment includes IUI (intra-uterine insemination) and, when that fails, IVF. The woman's age also plays an important role in successful conception, and age-associated infertility is probably the single most common form of "unexplained" infertility.
If these tests are all normal, then one could pursue less common causes of infertility, such as endometriosis, but the current approach is to focus on treatment rather than research of esoteric factors. The entry level treatment includes IUI (intra-uterine insemination) and, when that fails, IVF. The woman's age also plays an important role in successful conception, and age-associated infertility is probably the single most common form of "unexplained" infertility.