The impact of infections and genetics on secondary sex ratio.

The secondary sex ratio (SSR), which reflects the proportion of male to female offspring at birth, is influenced by a complex interplay of multiple factors. This review delves into the current understanding of how infections and genetics contribute to variations in the SSR. The effects of infections on the SSR represent an intriguing intersection of biology and epidemiology. Research indicates that several infectious diseases, such as toxoplasmosis, coronavirus disease 2019, Spanish flu, acquired immunodeficiency syndrome and tuberculosis, can impact the SSR through mechanisms that are only partially understood. Genetics are also scrutinized in this review. Although their involvement in determining the SSR is debatable, various genetic factors have been studied. The influences of the Rhesus D heterozygous phenotype, major histocompatibility complex, corticosteroid-binding globulin deficiency, ethnicity, and consanguinity on SSR have been delineated. By amalgamating findings from diverse disciplines, this review aims to offer a comprehensive overview of the multifaceted impact of infections and genetics on SSR, pinpointing potential implications for reproductive biology and public health.