Does the Sex of the Firstborn Child Affect the Breast Cancer Risk and Survival: A Systematic Review and Meta-analysis of Over 1 Million Cases

When we pooled all available evidence, the sex of the firstborn child was neither associated with risk nor prognosis in breast cancer. Clinically, our findings are reassuring and important, especially in light of previous studies that recommended differential treatment and counseling based on the sex of the first child. Socially, our findings challenge conventional social stereotypes that regard male children as biologically superior to female children.