Taking birth control pills can sometimes be effective in preventing pregnancy, and sometimes it is difficult to achieve the effect of contraception. Taking birth control pills is a common contraceptive method used by women of childbearing age. When women take birth control pills correctly under the guidance of a doctor, they can inhibit ovulation and slow down the growth of the uterine lining, which is not conducive to the implantation of a fertilized egg, and can generally achieve contraceptive effects. Whether short-acting contraceptives, long-acting contraceptives or emergency contraceptives, they are not 100% effective, and there is a certain chance of contraceptive failure even if they are taken correctly. If a woman takes birth control pills in an incorrect way, such as taking an incorrect dosage, omitting birth control pills, taking pills at an incorrect time, and so on, it will often lead to contraceptive failure.