( a ) gametogenesis -> implantation -> fertilisation -> insemination -> gestation -> parturition
( b ) gametogenesis -> insemination -> parturition -> fertilisation -> gestation -> implantation
( c ) gametogenesis -> insemination -> fertilisation -> implantation -> gestation -> parturition
( d ) gametogenesis -> insemination -> implantation -> fertilisation -> gestation -> parturition
