Relative to birth control pills still two tablets will be more effective in treatment. This is due to the fact that with two tablets, it contains a larger dose. The main mechanism of action of this drug is to inhibit female ovulation or if there is ovulation, it can prevent the fertilized egg from implanting, so by taking two tablets of the dose, the effect may be stronger, and can achieve the effect of contraception. Because the concentration of the drug is relatively large, so the relative side effects may also be larger, taking this drug common side effects are mainly nausea, vomiting, headache. In addition, a small number of women may experience irregular vaginal bleeding, but the incidence of side effects is relatively low, occurring in only about 2% of women.