Pregnancy and use of the oral contraceptive pill reduce a woman's risk of developing ovarian cancer, according to a recent study from the University of Queensland and the Queensland Institute of Medical Research.
The study team, headed by Dr David Purdie, of the University's Department of Social and Preventive Medicine, surveyed 1679 women from Queensland, New South Wales and Victoria to determine factors which cause the disease.
In what Dr Purdie believes is the first study of its size and kind in Australia, 824 of the women who had been diagnosed with ovarian cancer were compared to the remaining 855 disease-free women who were selected at random from the electoral roll.
'The most consistent factors found to be associated with ovarian cancer related to women's reproductive and contraceptive histories,' Dr Purdie said.
'In particular, a reduced risk of ovarian cancer was found with increasing number of children and longer duration of oral contraceptive use.
'These factors prevent a woman from ovulating, which prompted the finding that risk of ovarian cancer increased proportionately to the total number of lifetime ovulatory cycles.'
Dr Purdie said the cumulative effect of the trauma and repair caused by ovulation could increase the risk of developing ovarian cancer.
'The implication is that anything that prevents a woman from ovulating, such as taking the oral contraceptive pill, being pregnant, or breastfeeding, will reduce her risk of developing ovarian cancer,' he said.
The study, conducted at the Queensland Institute of Medical Research, also found that tubal sterilisation or hysterectomy reduced the risk of ovarian cancer by up to 40 per cent.
'The reason for this was not clear,' Dr Purdie said. 'However, it was possibly due to the fact that after these operations, the ovaries are effectively blocked from any possible irritants that may come either from external sources, such as talc, deodorants, dyes, viruses or contraceptive chemicals, or from the uterus, such as endometriosis or menstrual blood.'
He said this hypothesis was supported by the finding that women who dusted their genitals with talcum powder were also more likely to get ovarian cancer.
Women who had smoked, were overweight or who had a family history of ovarian or breast cancer were also more likely to develop ovarian cancer.
More than 100 Queensland women die from ovarian cancer each year, with 200 to 300 new cases diagnosed annually.
Dr Purdie said there were no specific symptoms of the disease, which was most common in women in their 50s and 60s.
'As there is no effective screening procedure for the early detection of ovarian cancer, by the time it is diagnosed, it has usually spread throughout the body and the prognosis is not good,'he said.
'Preventing the disease by avoiding potentially harmful behaviour and undertaking possibly preventive measures could reduce the impact of this devastating disease on the community.'
For more information, contact Dr Purdie on (07) 3240 5992.
