Researchers examined cancer risk in nearly 5,000 Finish women who gave birth at least 10 times before 2010.
Over a three-decade period, there were 656 cases of cancer in these women, about 200 fewer cases than would be expected based on cancer rates in the general Finnish population, researchers said.
The rate of new cancer cases was 24 per cent lower among women who delivered 10 or more babies compared to those in the general population, they said.
The rate of new cancer cases for breast cancer and gynecological cancers, including ovarian and endometrial cancer (cancer of the uterus lining), was about 50 per cent lower in women with 10 or more deliveries, compared to the general population.
In the study, women who had 10 or more babies were about five years younger when they gave birth to their first child, compared to average Finnish women, said study researcher Dr Juha Tapanainen, of the Department of Obstetrics and Gynecology at Helsinki University Central Hospital.
It's known that becoming pregnant at a young age helps protect against breast cancer, Tapanainen said.
Many women in the new study who had 10 or more children were members of the Laestadian movement, which is part of the Lutheran Church in Finland, researchers said.
Women in this group are similar to average Finnish women in terms of their lifestyle, but their religion prohibits the use of contraceptives, 'LiveScience' reported.
Studies on the effect of hormonal contraceptives on cancer risk have been inconclusive, but some studies suggest that the contraceptives reduce the risk of ovarian and endometrial cancer.
Thus, it's possible that if Laestadian women in the study also took contraceptives, and still had multiple pregnancies, it would even further reduce their risk of these cancers, Tapanainen said.
The study also linked having 10 babies with a reduced risk of basal cell skin cancer, and an increased risk of thyroid cancer. The reason for this link could not be determined.