An Australian longitudinal community study involving over 1500 women found that risk of death overall was lower for women with children, and the risk of death progressively reduced with increasing number of children. While the exact cause for the reduced mortality demonstrated in this study is not clear, evidence points to several plausible explanations for this finding.
Robust evidence indicates that women with a history of pregnancy and breastfeeding have a lower risk of developing breast cancer due to reduced exposure to the hormones that cause breast cancer. Breastfeeding may further reduce this risk by promoting maturation of breast tissue in order to produce breast milk which may help prevent breast cells from becoming cancerous.
Scientific evidence also suggests that duration of lactation and breastfeeding may reduce the risk of cardiovascular disease. In a study of over 139,000 postmenopausal women it was found that increased duration of lactation was associated with lower rates of cardiovascular disease as well as lower risk of developing high cholesterol, high blood pressure, and diabetes.
These findings may account for the lower risk of mortality found in women who have had multiple children.
References:
1. Simons L, Simons J, Friedlander Y, McCallum J. Childbearing history and late-life mortality: the Dubbo study of Australian elderly. Age and Ageing. 2012;41(4):523-528.
2. Reproductive History and Cancer Risk [Internet]. National Cancer Institute. 2021 [cited 4 May 2021]. Available from: https://www.cancer.gov/about-cancer/causes-prevention/risk/hormones/reproductive-history-fact-sheet
3. Schwarz E, Ray R, Stuebe A, Allison M, Ness R, Freiberg M et al. Duration of Lactation and Risk Factors for Maternal Cardiovascular Disease. Obstetric Anesthesia Digest [Internet]. 2010;30(2):106-107. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2714700/