Parity and breastfeeding are preventive measures against breast cancer in Iranian women

Breast cancer (BC) is the most prevalent cancer in Iranian women and the fifth most common cause of cancer-related death in Iran. Among predicting factors and preventive measures for BC, the parity and breastfeeding (BF) are controversial issues. We therefore conducted this case-control study to find out the relation of parity and BF to incidence and risk of BC.

A structured questionnaire that covered demographic criteria and BC risk factors was completed for case (376 cases) and control (425 subjects) groups, both matched in terms of demographic variants, reproductive issues, and socioeconomic status. Odds ratio (OR) and 95% confidence intervals (CI) were computed as measures of association from the logistic models. All p values reported are two-sided.

Parity significantly reduces the risk of BC (p < 0.001, OR 2.05, CI 1.4-3.3), and BF is protective (p = 0.0001, OR 0.39, CI 0.27-0.56). The best result was gained with 1-3 parity and 24 months BF and mean duration of 18-24 months per child (p = 0.037, OR 0.7, CI 0.5-0.98).

On the basis of breast anatomical and physiological changes during pregnancy, and parity and breastfeeding, full-term pregnancies and parities with efficient BF significantly reduced the risk of breast cancer compared with nonpregnant and nulliparous women or those who never breastfed. The number of children should ideally be limited to 1-3, and the cumulative duration of BF not less than 25-36 months. We would recommend 1-3 pregnancies and a BF duration not less than 18 months, with best results being achieved with 24 months per child.