Here is the translation of the provided content into English: "Consecutive two menstrual cycles with reduced flow are caused by what reasons"

Patient's question:

I am a college student, female, only 23 years old. I am always worried about irregular menstruation affecting future fertility, and I feel embarrassed going to the hospital. Could you please tell me: What are the reasons for having less menstrual flow for two consecutive periods?

Doctor's answer:

First, you need to clarify how you truly have a low menstrual flow. The menstrual cycle is generally 3-7 days, with a flow of 30-80 milliliters per period. The menstrual cycle is normal, with bleeding time less than 2 days, and flow less than 20 milliliters. It is usually believed that this is a case of hypomenorrhea. Hypomenorrhea is similar to hypermenorrhea in that both are abnormal phenomena. The causes of hypomenorrhea are similar to those of amenorrhea, except that the extent is different. The reasons are roughly as follows:
(1) Physiological: Due to hereditary factors across generations or interference from environmental factors.
(2) Pathological:
① Congenital uterine underdevelopment, where the uterus is very small, with only a very small amount of endometrium shedding, resulting in low menstrual flow.
② Ovarian hypoplasia, where there are two types of special granules in the endometrial cells called lysosomes, which are related to menstrual blood volume and bleeding time.