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An international study has shown that having more than one child dramatically lowers the chance of developing cancer for women carrying breast cancer gene mutations.

The International BRCA1/2 Carrier Cohort Study (IBCCS) examined the effect of pregnancy, birth and breastfeeding on women with cancer-causing mutations in the BRCA1 and BRCA2 genes, who have an increased risk of developing breast cancer.

The study, reported in Medical News Today, found that while one pregnancy and birth had no effect on subsequent cancer development for those carrying the mutant genes, a woman’s risk of developing breast cancer was lowered substantially when she had more than one child.

Breast cancer rates in women over age 40 dropped 14 per cent with every additional child born.

The study also found a difference in cancer development based on the timing of a woman’s first child.

Women carrying the BRCA2 mutation doubled their risk of developing cancer when they had their first child after age 20, compared to those who gave birth before age 20.

For women carrying the BRCA1 mutation, the opposite was true: women who delayed the birth of their first child until after age 30 lowered their risk of developing breast cancer.

Participants in the study all carried a breast cancer gene mutation.

853 had developed breast cancer.

The IBCCS study was carried out by researchers in France, the U.K., the Netherlands, Sweden, Germany and Canada. The German Cancer Research Center, Deutsches Krebsforschungszentrum (DKFZ), played a key role in the study.

[Medical News Today, 31May06,Gudrun Schultz,]