dear lady, your medication contains progesterone which is a hormone that upon withdrawal from body will cause menses. since the duration the effects of this hormone remain in body are more than a day, missing a pill wont bring menses. it usually takes 3-5 days of stopping the pill for menses to come. that is the reason, the pill is prescribed only from day 1- day 21 to maintain a proper 28-30 days menstrual cycle. there would be no adverse consequences of missing this pill for a day. however, it should be taken again as soon as remembered, just like you did, to avoid any chances of accidental pregnancy. it would usually not affect your menses. this drug is well known for regularising menses and providing birth control but it does have side effects like weight gain, salt water retention and irritable mood (it subsides in 5-7 days). the benefits, however, outweigh the risks. so carry on with the advice of your gynaecologist. regards!