fertile period, the time in the menstrual cycle during which fertilization may occur. Spermatozoa can survive for approximately 5 days; the ovum lives for approximately 24 hours. Thus the fertile period begins up to approximately 6 days before ovulation and lasts for approximately 1 day afterward. It may be identified by observation of the changes in the quantity and character of the cervical mucus or changes in the basal body temperature, or it may be determined from a calendar record of six or more menstrual cycles, applying the knowledge that ovulation usually occurs 14 days before menstruation.
