The menstrual cycle is the monthly hormonal process a woman's body goes through to prepare for a possible pregnancy. Regular menstrual periods in the years between puberty and menopause are usually a sign that your body is working normally. Irregular or heavy, painful periods are not normal. Many women also get premenstrual syndrome (PMS) symptoms. Source: Office on Women's Health
Menstruation, or period, is normal vaginal bleeding that occurs as part of a woman's monthly cycle. Every month, your body prepares for pregnancy. If no pregnancy occurs, the uterus, or womb, sheds its lining. The menstrual blood is partly blood and partly tissue from inside the uterus. It passes out of the body through the vagina. Source: MedlinePlus
A normal menstrual cycle ranges from 21 to 35 days, with bleeding typically lasting 2 to 7 days. For the first few years after menstruation begins, long cycles are common. However, menstrual cycles tend to shorten and become more regular as people age. Source: Mayo Clinic
The menstrual cycle consists of four main phases: menstrual (shedding of the uterine lining), follicular (egg maturation and uterine lining buildup), ovulation (release of an egg), and luteal (maintenance of the uterine lining). Source: American College of Obstetricians and Gynecologists (ACOG)
Ovulation typically occurs about 14 days before a woman's period begins. The fertile window is the period during which pregnancy is possible, usually spanning 5 days before ovulation and the day of ovulation. Source: Planned Parenthood
Premenstrual syndrome (PMS) involves physical and emotional symptoms before a period, while premenstrual dysphoric disorder (PMDD) is a more severe form with marked mood symptoms and functional impairment. Source: MedlinePlus
Cycles outside 21–35 days, bleeding longer than 7 days, very heavy flow, bleeding between periods, or missing 3 periods in a row warrant medical advice. Source: Mayo Clinic
It’s less likely but possible—especially with short cycles or early ovulation—because sperm can survive for several days. Source: NHS
Cramping (dysmenorrhea) is common; severe, worsening, or prolonged pain can signal conditions like endometriosis or fibroids—seek care if pain is severe or lasts beyond a few days. Source: Cleveland Clinic
Amenorrhea is absence of periods: primary (no first period by ~age 15) or secondary (periods stop for 3+ months in someone who previously menstruated). Some causes are normal (pregnancy, breastfeeding, menopause) while others need evaluation. Source: NHS
Menarche usually occurs around ages 12–13 (range varies); menopause typically occurs between 45–55, with an average near 51. Source: ACOG
Age (puberty, perimenopause), stress, significant weight change, intense exercise, some contraceptives, thyroid or PCOS and other health conditions can alter timing and flow. Source: NHS