Short-acting oral contraceptives are usually composed of oestrogen and progestin, and are often taken on a cyclical basis to regulate menstruation, but some users with normal periods may experience abnormalities such as low menstrual flow.
On the other hand, if oral contraceptive pills are not taken on a regular cycle, they may also lead to menstrual disorders. If necessary, the pill can be stopped and the menstruation observed to return to normal. If the low menstrual flow persists, you should seek medical advice.
Emergency contraceptives, which are generally high in hormones, also tend to cause low menstrual flow or cycle disruption and should not be used as a regular contraceptive.