Hi, There may be a change in hormonal levels of the system when Microgestin is taken instead of Loestrin. Cycles may get disturbed after a change of dose or brand of any birth control pill causing disturbed cycles, early or late period, short or long period, spotting, intermittent bleeding, etc. due to hormonal fluctuations, that may settle down in a couple of months. Taking the missed pill as soon as remembered or taking 2 pills the next day if a pill is missed is the ideal recommendation to maintain contraception. However, this may lead to hormonal changes sometimes causing cycle disturbances. If a similar patient comes to my clinic, I would recommend waiting and watching for the period to stop and continuing the birth control pack. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Divya Teja Pasupuleti, General & Family Physician