Current hypotheses do not explain the concerns about sex ratio modulation at conception, birth or during life, and particularly about sex ratio reversal, e.g. at very young or advanced maternal age, during 'anovulatory seasons', among those of low socio-economic status, or induced by specific lifestyles, etc. These modulations are explained by the introduction of the ovopathy concept and inherent preferential fertilization of non-optimally matured oocytes by Y-bearing sperm. Non-optimal development and implantation of male-biased fetuses results in perennial loss of non-optimal, male-biased fetuses before and after birth. Accumulation of conceptopathology in extreme conditions entrains an increasing male to female ratio and ultimately a decreasing one, i.e. an 'inverted dose-response gradient' or 'dose-response fallacy'.