A 48-year-old woman tells the nurse, "I missed my period last month. Am I in menopause?" The nurse knows that at which point is a woman considered to be menopausal?

A. Her periods have been irregular and light for 12 months: Irregularity and lighter flow are features of perimenopause but do not by themselves meet the definition of menopause. B. She experiences symptoms of decreased estrogen, such as dyspareunia: Symptoms such as vaginal dryness or dyspareunia suggest decreased estrogen but are not diagnostic of menopause without the 12-month amenorrhea criterion. C. Her periods have stopped for 1 year: Menopause is defined clinically as 12 consecutive months of amenorrhea (absence of menses) not due to other causes. D. She has symptoms of vasomotor instability: Hot flashes and night sweats are common during menopause but their presence alone does not establish the diagnosis without the period of amenorrhea.