Female infertility may result from problems localized to the female genitalia or from systemic conditions. One of the most common causes are problems affecting the fallopian tubes, as well as ovulation disorders. Endometriosis, which is characterized by the development of endometrial tissue outside the uterus, affects 10% to 15% of women during their reproductive years; also, female fertility decreases with age. This decline begins after the age of 30, it becomes more evident after 35 and obviously more serious after 40; however, this does not mean that women do not conceive naturally at 42 or even 45 years of age.
Other factors may be associated with endocrine disorders, which usually affect ovulation and other processes, thereby also affecting fertility, e.g. diabetes, thyroid disease, adrenal gland disorders, etc.); cervical problems (e.g., the cervix and the cervical mucus are "unfriendly" to the passage of sperm due to immunological factors, the presence of a cervicitis, etc.); problems with the endometrium (hyperplasia, presence of fibroids, polyps, or adhesions due to a previous dilation and curettage (D&C) procedure, etc.); uterine problems due to a congenital malformation of the uterus, which may be too small, or bicornuate (two-horn shaped), or septated (comprising two cavities), etc.; these are treated as appropriate. Finally, there are psychological factors such as stress, pressure at work, fatigue etc., playing an important role in conception. However, experts agree that usually these are temporary factors.