- A highly effective method of birth control is defined as one that results in a low failure rate (i.e., <1% per year) when used consistently and correctly, such as condom + diaphragm, condom + spermicide, diaphragm + spermicide, or intrauterine device [IUD] with documented failure rate of <1% per year, or oral/injectable/implanted hormonal contraceptives used in combination with a barrier method.