Stopping mid-cycle, causes loss of all benefits. If you had been using them to regulate your period, soon your period will go back to the way it was before pills. Stopping birth control will also put you back at the risk of getting pregnant. Also as soon as you stop, your period should come in a few days.
The biggest risk that you run is of conception. If you stop taking your pills mid-cycle and do not wish to concieve, you should resort to a backup method of contraception. If your doctor prescribed the BCP for a reason besides contraception, you should disclose your decision to stop.
The biggest risk is that you may become pregnant, since you typically ovulate mid-cycle. If you are taking birth control periods to regulate your periods, you may also experience more pain during menstruation and a longer cycle than while on the pill due to different levels of hormones.
The major risk is pregnancy. If you stop mid-cycle, you leave yourself open to fertilization. Also, it changes your cycle, and can often cause rapis weight gain/loss, cramping, and other PMS symptoms.