Microgynon 30 is a combined monophasic pill containing progesterone and estrogen. It has to be taken daily for 21 days. The 7 day break after each pack will result in hormonal withdrawal resulting in menstruation. The next pack must be immediately started on the 8th day. This will ensure regular cycles of 28 days with effective contraception.
Using back to back packs without break will delay your period as it is necessary to have a hormone free period of few days for menstruation to occur. If you want to start your regular cycle a bit early (3 days in your case), you can do that by shortening the break to 4 days. But shortening the 21 pill course should not be done even by a single day as you will not contraceptive protection by doing so. Each missed pill for more than 12 hours should be followed by a 7 consecutive days of pills before you can be safe. You must use other barrier methods or abstain from sex in the meantime. So, I advise you to shorten the break period rather than pill period, if you want to have you cycle start 3 days early. Taking 21 pills consecutively is absolutely essential for effective contraception.
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