Childbirth and contraceptives have significantly reduced the risk of ovarian cancer by tens of percent.

The authors of the scientific paper, published in the journal International Journal of Gynecological Cancer, utilized machine learning to explore the correlation between ovarian cancer and various other factors. The research was conducted using data from 222,000 women from the UK Biobank who had encountered cancer. To eliminate false correlations, the researchers applied logistic regression with multiple variables.

As a result, it was discovered that women who had given birth to two or more children faced this oncological condition 39% less frequently than those who had never given birth. However, this information is hard to label as truly novel: Naked Science previously discussed in detail why women and men with biological children suffer from all types of cancer less often than those without children (and the likelihood is even lower for those with multiple children compared to those with fewer).

Furthermore, the scientists demonstrated that women who used contraceptives developed ovarian cancer 26% less frequently than those who did not. Moreover, if oral contraceptives were used after the age of 45, the likelihood of such a disease decreased even further—by 43%. The authors of the new study made significant efforts to isolate other factors that could influence this correlation but were unable to identify them. Therefore, they believe that there is a causal relationship: fewer ovulations, in their view, reduce the probability of ovarian cancer.

At the same time, the researchers did not investigate how the likelihood of using contraceptives correlates with the number of children in the family. Other studies indicate that married women are significantly more likely to use oral contraceptives than those who are not married. In other words, the conclusions of the new study regarding contraceptives require a more careful separation from the influence of childbirth on the likelihood of ovarian cancer.

The authors also noted that being overweight correlates with a slightly increased risk of this disease (up to 28%). In light of all this, the researchers suggested that the risk of ovarian cancer could potentially be reduced—specifically, by managing weight and the number of ovulations. Interestingly, they did not suggest influencing the number of births, likely considering this factor to be practically unmodifiable.

The situation with cancer is attracting increasing attention from the scientific community, as due to modern lifestyles, the probability of cancer diseases among people is rising, while the average age of onset is decreasing. Therefore, despite progress in treating this disease, it continues to be the leading cause of mortality in developed countries. Over time, this situation is expected to worsen.