Oral contraceptives and risk of breast cancer.

Use of oral contraceptives (OCs) by women before age 25 or first full-term pregnancy has been theorized to increase the risk of breast cancer. While multiple studies have reported a positive relationship between early use and subsequent breast cancer development, numerous researchers have concluded there is no effect. One reason for the varied results may be the case control methodology utilized by the majority of studies and its associated biases including selection, information, and recall bias. Other theories include an undetected latent effect, changing dosages and formulations, earlier breast cancer diagnosis and follow-up among OC users, and chance. While more research is needed, the weight of evidence supports no increased risk of breast cancer among OC users, including women less than 25 years of age and before first full-term pregnancy. Hence, it seems unnecessary to change the current approach toward OC use.