Do oral contraceptives increase the risk of developing cancer?

Large population studies have shown that the use of combined oral contraceptives (i.e. containing oestrogens and progesterones) increases the risk of some cancers and lowers the risk of others. Women who take oral contraceptives, or who have used them in the past 10 years, have a slight increase in breast cancer risk. 

Research indicates oral contraceptives increase the risk of cervical cancer, but only in women who already have the human papillomavirus (HPV), which causes almost all cervical cancers. For both breast and cervical cancers, the risk starts to decline when you stop taking oral contraceptives. Ten years after stopping, the risk is the same as that of women who have never taken oral contraceptives. 

Oral contraceptives have been shown to be protective against ovarian cancer and endometrial cancer, with the protection increasing with the length of time the pill is taken and lasting for decades after stopping use. On balance, the strong evidence of reduced lifetime risk of endometrium and ovarian cancer outweighs the temporary risks associated with breast and cervical cancer. As for any prescription medication, they should be taken as recommended by your doctor. Women who are over 40 and have completed their families, may like to consider other forms of contraception.