Menstrual cycle The first period usually begins between twelve and fifteen years of age, a point in time known as menarche. They may occasionally start as early as eight, and this onset may still be normal. The average age of the first period is generally later in the developing world and earlier in developed world. The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women and 21 to 35 days in adults (an average of 28 days). Menstruation stops occurring after menopause which usually occurs
Menstrual cycle extra-pair flirtations and demonstrate a preference for extra pair copulation. Preferences for voice pitch change across the cycle. When seeking a short term mating partner, women may prefer a male with a low voice pitch, particularly during the fertile phase. During the late follicular phase, it is common for women demonstrate a preference for mates with a masculine, deep voice. Research has also been conducted on the attractiveness of the female voice throughout the cycle. During their most fertile phase of the menstrual cycle, there is some evidence that female voices are rated as significantly more attractive. This effect is