• Jessica Fields, MD, FACOG

The Basics of the Menstrual Cycle



MENSTRUAL CYCLE QUICK FACTS

  • The median age at menarche (the fancy word for when you start your period) is between 12-13.

  • Menstrual cycle interval is typically between 24 and 38 days (all menstrual cycles do not last 28 days!)

  • Periods can become irregular due to stress or sickness. They become irregular again as we get closer to menopause.

  • Menstrual flow length definitely varies, however, generally lasts up to 8 days.

  • Average menstrual product use: 3-6 pads or tampons per day

PRO TIP: Keep track of your menstrual cycle before visiting your ob/gyn (dates, length, type of bleeding). This will help to advocate for yourself if you think your period has changed.

THE PHASES OF YOUR MENSTRUAL CYCLE


PHASE 1 - The menstrual phase

  • When you get your period because an egg isn’t fertilized and hormone levels drop.

  • The thickened lining of your uterus is no longer needed so it sheds and you release blood, mucus, and tissue. Common symptoms include cramps, bloating, mood swings, tiredness, headaches, tender breasts, etc.

PHASE 2 - The follicular phase

  • This starts on the first day of the period (overlaps with menstrual phase) and ends with ovulation.

  • The hypothalamus (a structure deep in the brain) signals the pituitary (the master gland just below the brain) to release follicle-stimulating hormone (FSH), which stimulates the ovaries to produce follicles containing immature eggs.

  • One (or occasionally more) egg will mature and this causes estrogen to increase and thicken the lining of the uterus. The follicular phase can last 11-27 days (average 16).

PHASE 3 - Ovulation

  • This is when your ovary releases an egg which can be to be fertilized by sperm. If you’re trying, you’ll know this is the time you can get pregnant. Usually about the middle of the menstrual cycle, however it can vary.

PHASE 4 - Luteal phase

  • After the follicle releases an egg, it will change into the corpus luteum and release hormones (mainly progesterone) to keep the uterine lining thick and allow for implantation of a fertilized egg. If you don’t get pregnant, the corpus luteum will get smaller and be reabsorbed which causes the hormone levels to drop off and you ultimately get your period.


QUICK FACTS BLOATING & YOUR CYCLE

About 70% of women experience bloating during their period due to fluctuations in estrogen levels and a decrease in progesterone right before periods. THE SCIENCE: When estrogen levels are high, the body retains water.


TIPS: To combat bloating, continue working out, decrease alcohol + caffeine, stay away from food that leads to gas, take anti-inflammatories over the counter like ibuprofen, avoid fizzy beverages, sleep.



I’M ON HORMONAL BIRTH CONTROL, WHAT ABOUT MY “PERIOD”?

There’s a lot of confusion about pill bleeds so here’s the science behind them. No, they’re not your period!!!


Put simply, with normal menstruation, the uterine lining thickens in preparation for a possible pregnancy. If there is no pregnancy, this lining will shed. In contrast, with hormonal birth control, halting the addition of hormones causes a small amount of bleeding that is usually light and short - it does not contain uterine lining. You can still have period-like symptoms, e.g. bloating, breast tenderness, diarrhoea or constipation, headaches, mood changes. It can be known as Withdrawal Bleeding vs. a period.


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