During each menstrual cycle, an egg is produced and released from the ovaries. The lining of the uterus thickens. If pregnancy does not occur, the uterine lining sheds during menstruation. Then, the cycle begins anew.
The menstrual cycle is divided into four phases:
- menstrual phase
- follicular phase
- ovulatory phase
- luteal phase
The duration of each phase may vary and change over time.
Menstrual Phase
The menstrual phase is the first phase of the menstrual cycle. It is also the time when you have your period.
This phase begins when an egg from the previous cycle fails to be fertilised. Since pregnancy has not occurred, levels of the hormones estrogen and progesterone decrease.
The thick lining of the uterus—which serves to support a pregnancy—is no longer needed; therefore, it breaks down and is expelled through the vagina. During your period, you expel a combination of blood, mucus, and tissue from the uterus.
You may experience menstrual symptoms such as:
- muscle aches (try these home remedies)
- breast tenderness
- bloating
- mood swings
- irritability
- headaches
- fatigue
- lower back pain
Follicular Phase
The follicular phase begins on the first day of your period (so there is some overlap with the menstrual phase) and ends when you ovulate.
It begins when the hypothalamus signals the pituitary gland to release follicle-stimulating hormone (FSH). This hormone stimulates the ovaries to produce 5-20 small sacs called follicles. Each follicle contains an immature egg.
Only the healthiest eggs will reach maturity. (In exceptional cases, a woman may have two mature eggs.) The body reabsorbs the remaining follicles.
The maturing follicle triggers a sudden surge in estrogen, which thickens the lining of the uterus. This creates a nutrient-rich environment conducive to embryo development.
The follicular phase lasts an average of about 16 days. This period can range from 11 to 27 days, depending on your cycle.
Ovulation Phase
The rise in estrogen levels during the follicular phase stimulates the pituitary gland to release luteinizing hormone (LH). This initiates the process of ovulation.
Ovulation is the moment when the ovary releases a mature egg. The egg travels down the fallopian tube toward the uterus, where a sperm fertilizes it.
The ovulation phase is the period of the menstrual cycle during which conception is possible. You can identify when you are ovulating through symptoms such as the following:
- a slight increase in basal body temperature
- thicker discharge with a texture similar to that of egg whites
Ovulation typically occurs around day 14 if you have a 28-day cycle—that is, at the midpoint of your menstrual cycle. It lasts approximately 24 hours. After 1 day, the egg dies or dissolves.
Luteal Phase
After the follicle releases its egg, it transforms into the corpus luteum. This structure releases hormones—primarily progesterone and some estrogen. The rise in these hormones keeps the uterine lining thick and prepared for the implantation of a fertilized egg.
If you become pregnant, your body will produce human chorionic gonadotropin (hCG). This is the hormone detected by pregnancy tests. It helps sustain the corpus luteum and maintains the thickness of the uterine lining.
If you do not become pregnant, the corpus luteum will shrink and be reabsorbed. This causes a drop in estrogen and progesterone levels, which triggers the onset of your menstrual period. The uterine lining sheds during your period.
During this phase, if you do not become pregnant, you may experience symptoms of premenstrual syndrome (PMS). These include:
- bloating, breast pain, or tenderness
- mood swings
- headaches
- weight gain
- changes in sex drive
- food cravings
- difficulty sleeping
The luteal phase lasts from 11 to 17 days. The average duration is 14 days.
Identifying Common Problems
Every menstrual cycle is different. Some people get their period at the same time every month; others are more irregular. Some experience heavier or longer-lasting bleeding than others.
Your menstrual cycle can also change at certain times in your life. For example, it may become irregular as you approach menopause.
One way to determine if you have any issues with your menstrual cycle is to keep a record of your periods. Note when they start and when they end. Also, record any changes in the amount of bleeding or the number of days your period lasts, as well as whether you experience spotting between periods.
Any of the following factors can alter your menstrual cycle:
- Birth control pills can make your periods shorter and lighter. While taking certain pills, you may not get your period at all.
- Your periods should stop during pregnancy. A missed period is one of the most obvious early signs that you are pregnant.
- Polycystic Ovary Syndrome (PCOS). This hormonal imbalance prevents the normal development of eggs in the ovaries. PCOS causes irregular menstrual cycles and missed periods.
- Uterine Fibroids. These non-cancerous growths in the uterus can make your periods longer and heavier than usual.
- Eating Disorders. Anorexia, bulimia, and other eating disorders can disrupt your menstrual cycle and cause your periods to stop.
Here are some signs of a problem with your menstrual cycle:
- You miss your period, or it stops completely.
- Your period is irregular.
- You bleed for more than 7 days.
- The interval between your periods is less than 21 days or more than 35 days.
- You bleed between periods (heavier bleeding than just spotting).
If you experience these or other problems with your menstrual cycle or periods, consult a healthcare professional.
Points to Remember
Every menstrual cycle is different. What is normal for you may not be normal for someone else.
It is important to know your cycle well, including when your period starts and how long it lasts. Pay attention to any changes and report them to a healthcare professional.
Also Read: Prenatal Yoga: Supporting Mother and Baby, Gently