The association of reproductive factors with risk of non-epithelial ovarian cancer and comparison with serous ovarian cancer.

Objective: To examine the association between reproductive factors and risk of non-epithelial ovarian cancer and to compare the associations with those in serous ovarian cancer.

Methods: From the Danish Cancer Registry, we identified all ovarian cancer cases (≥20 years old at diagnosis) of germ cell (n = 188), sex cord-stromal (n = 116), or serous (n = 4854) histology during 1982-2016. For each case, 15 age-matched female controls were selected with risk set sampling.