title: The ovulation method--vulvar observations as an index of fertility/infertility.
mesh_terms: D002582:Cervix Mucus; D005260:Female; D005298:Fertility; D006801:Humans; D007247:Infertility, Female / Q000175:diagnosis*; D008598:Menstruation; D008954:Models, Biological; D012252:Natural Family Planning Methods; D010060:Ovulation; D014844:Vulva