It has been known for some time that there is a link between the use of the combined oral contraceptive pill and a reduced risk of ovarian cancer. The authors of this 2018 study argue that many of the earlier studies did not include large numbers of women using more recent contraceptives, such as long-acting progestogen-only methods, newer progestogens in oral combined pills such as drosperinone, gestodene and cyproterone, and alternative routes of administration such as the vaginal ring. As many women are now using these newer methods, it is important that data be available.1

This was a prospective nationwide cohort study conducted in Denmark between 1995 and 2014. The study, which is part of the Danish Sex Hormone Register Study, linked data from Danish women aged 15–49 between 1995 and 2014, with women excluded if they had emigrated, had cancer, had deep vein thrombosis, or were treated for infertility before entering the study. Data linked from the Danish government included prescriptions for hormonal contraceptives, cancer diagnoses, hospital admissions and surgeries, and birth statistics. The study included data from over 1.8 million women.

More than 20 million person-years of data were available. There were 1249 ovarian cancers recorded, with 771 cancers in the women who had never used hormonal contraceptives (with an exposure of 13 million person-years), and 478 cancers in the group of women who had used hormonal contraception (with an exposure of 8 million person-years). Compared with women who had never used hormonal contraception, reduced risks of ovarian cancer were observed with current or recent use (RR=0.58; 95% CI 0.49 to 0.68) and former use of any hormonal contraception (RR=0.77; CI 0.66 to 0.91), respectively. Relative risks among current or recent users decreased with increasing duration (from RR=0.82; CI 0.59 to 1.12 with less than one years’ use to RR=0.26; CI 0.16 to 0.43 with more than 10 years’ use; P<0.001 for trend). There was no reduced risk of ovarian cancer associated with the use of progesterone-only contraceptives.2