摘要：Secondary sex ratio (SSR) is defined as the ratio of number of males to females at birth and is considered a meaningful end point for indicating adverse effects of environmental exposures (Organisation for Economic Co-operation and Development 2018). The SSR in humans has been relatively stable over time in showing a slight male excess in births (51.4%) (James 2008). However, in recent years, some industrialized nations have witnessed a decline in SSR (Chao et al. 2019). Reasons for variability in the SSR are unclear. A prevailing hypothesis is that exposure to endocrine-disrupting chemicals in animals and humans influences SSR via changes in periconceptional hormonal concentrations (James 1987). Nevertheless, human studies of periconceptional exposure to endocrine-disrupting compounds and SSR have produced inconsistent results (Terrell et al. 2011).
