What is the reason for less and darker menstrual flow after taking birth control pills?

Patient's question:

No

Doctor's answer:

Generally speaking, it is normal to have brown or black vaginal discharge 1-2 days before and after the end of menstruation, but the causes are different. Black discharge before menstruation is caused by the shedding of a small amount of endometrium, while black discharge after menstruation is due to blood remaining in the reproductive tract for too long.