Amenorrhea is the absence of menstruation. In girls before adolescence, in women during pregnancy and lactation as well as during and after menopause, amenorrhea is expected and it is normal (normal amenorrhea).
Primary amenorrhea is the condition in which non-menstruation occurs and is considered abnormal if the girl does not menstruate and does not develop secondary sexual characteristics by the age of 14 or if she has a normal development of secondary sexual characteristics and has no menstruation until the age of 16 years.
Secondary amenorrhea is defined as the absence of menstruation for six consecutive months in a woman who has previously had normal cycles (excluding periods of normal amenorrhea).
10-20% of women with infertility problems develop amenorrhea and it often occurs (up to 50%) in long-distance athletes (high-level athletes who run more than 100 kilometers per week).