What is the most common cause of secondary amenorrhea?

The most common cause of secondary amenorrhea is pregnancy. Secondary amenorrhea refers to the absence of menstruation for three consecutive cycles or more in a woman who previously had a normal menstrual cycle. Pregnancy is the primary consideration when a woman experiences secondary amenorrhea, as it is a physiologic state where menstruation ceases.

In evaluating a patient with secondary amenorrhea, ensuring that pregnancy is ruled out is a critical first step in diagnosis. This can typically be done through a home pregnancy test or a serum pregnancy test, which is highly sensitive and specific in detecting human chorionic gonadotropin (hCG) levels associated with pregnancy.

Other factors, like menopause, obesity, and excessive exercise, can certainly contribute to secondary amenorrhea. Menopause typically occurs later in life and leads to the end of menstruation but is not a common cause in younger women. Obesity can lead to hormonal imbalances affecting the menstrual cycle, and excessive exercise can result in similar hormonal effects; however, these are less prevalent as causes compared to pregnancy. Therefore, confirming pregnancy is essential in assessing secondary amenorrhea and is why it is considered the most common cause.