If the oral short-acting contraceptive pill is taken orally, starting on the third day of menstruation, with a total of 21 tablets, that is, all the pills are taken on the twenty-fourth day of menstruation, this situation will cause the following clinical consequences: 1, shorten the menstrual cycle. 2, because the contraceptive pills tend to be started on the fifth day of menstruation so that they can effectively inhibit ovulation of the ovaries, and if they are taken on the third day, the inhibition of If taken on the third day, it is likely that the time of ovulation inhibition will be changed, so it is recommended that it is best to start taking it only on the fifth day of menstruation. It is recommended to take it orally at a fixed time every day during the period of taking it, so that the contraceptive effect will be better. The 21-day oral contraceptive pill will only provide contraception for 1 month. If contraception is needed for the next month, start taking it again from the fifth day of menstruation.