postovulatory (premenstrual) phase is the time between ovulation and the onset of the menses and normally lasts 14 days. During this phase the ovum travels through the fallopian tubes to the uterus. If the ovum becomes fertilized during this passage, it will become implanted in and nurtured by the newly developed endometrial lining. However, if fertilization does not take place, the lining deteriorates and eventually sloughs off, marking day 1 of the next cycle.
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2. American Academy of Orthopacdic Surgeons: Emergency Care and Transportation of the Sick and Injured, ed 3.