The risk for developing ovarian cancer appears
to be affected by several factors.
The more children a woman has, the lower her
risk of ovarian cancer. Early age at first pregnancy, older ages
of final pregnancy and the use of low dose hormonal contraception
have also been shown to have a protective effect. Ovarian cancer
is reduced in women after tubal ligation.
The link to the use of fertility medication,
such as Clomiphene citrate, has been controversial.
An analysis in 1991 raised the possibility that
use of drugs may increase the risk for ovarian cancer. Several cohort
studies and case-control studies have been conducted since then
without providing conclusive evidence for such a link.  It will
remain a complex topic to study as the infertile population differs
in parity from the "normal" population.
There is good evidence that in some women genetic
factors are important. Carriers of certain mutations of the BRCA1
or the BRCA2 gene, more frequent in some populations (e.g. Ashkenazi
Jewish women) are at a higher risk of both breast cancer and ovarian
cancer, often at an earlier age than the general population.
Patients with a personal history of breast cancer
or a family history of breast and/or ovarian cancer, especially
if at a young age, may have an elevated risk.
A strong family history of uterine cancer, colon
cancer, or other gastrointestinal cancers may indicate the presence
of a syndrome known as hereditary nonpolyposis colorectal cancer
(HNPCC, also known as Lynch II syndrome), which confers a higher
risk for developing ovarian cancer. Patients with strong genetic
risk for ovarian cancer may consider the use of prophylactic oophorectomy
after completion of child-bearing.