Understanding Your Menstrual Cycle

Do you track your periods? There are benefits of tracking every phase of your menstrual cycle. The more you know, the better you can take control of your reproductive health.

Menses

Your menstrual cycle begins on the first day of your period. Your estrogen and progesterone levels drop, which triggers your uterus to shed its lining. For most women, their period lasts one to seven days; five days is the average. Anything lasting longer than seven days is considered heavy menstrual bleeding.

First Phase: Follicular Phase

Your cycle is divided into two phases: the follicular and the luteal phase. The start of the follicular phase coincides with day one of your menses; your period is part of the follicular phase. Throughout this time, an egg is maturing inside one of the fluid-filled sacs inside your ovaries. All the while, your body is producing follicle-stimulating hormone, or FSH. The FSH is responsible for activating your ovaries to start producing follicles. With each cycle, one follicle will become dominant, ready to release an egg. That follicle, in turn, produces estrogen that causes a thickening of your uterus lining, ready in case a fertilized egg implants there.

Mid-Follicular Phase

During this time, your cervical mucus changes to become thinner, more fluid and elastic, like an egg white.

For those who are regular and rely on natural family planning, this is when you want to avoid sex or use a condom. However, know that the natural family planning method is only 60% effective.

Ovulation

When the follicle releases the egg, you ovulate. In women who are very regular, ovulation occurs 15 days after your period has started. The follicle ruptures when it releases the egg, and for some women, this can be painful.

Second Phase: Luteal Phase

Next, the dominant follicle that released the egg transitions into what is called a corpus luteum. This serves as a temporary endocrine gland that produces progesterone.

During this time, your cervical mucus changes to become thicker.

This phase starts from the moment the follicle ruptures – ovulation – and ends when your period begins. During this phase, your progesterone levels increase, stimulating the thickening and secretory glands of the uterus. This readies the uterus to receive the embryo if fertilization happens.

This delicate balance between estrogen and progesterone levels is responsible for the discomfort in your cycle, including:

• Mood swings
• Breast tenderness
• Bloating
• Fatigue

With birth control pills, hormone levels stay constant and these symptoms can significantly improve.

If there is an embryo, your body starts to create a hormone called Human chorionic gonadotropin, or hCG. This hormone:

• Signals the body that pregnancy has occurred
• Maintain the corpus luteum until the placenta is ready 
• Stimulates the corpus luteum to produce progesterone
• Helps keep the pregnancy viable and helps the fetus develop

What You Need To Know

The most important thing to know is what is normal for you regarding the length of your period, as well as how many days are in between menses. For women younger than 18 or older than 45, it can be harder to track your periods as your menses are likely irregular.

Tracking Fertility

For many women, the biggest advantage to tracking your cycle is pinpointing your fertility window, which is helpful whether you are trying to conceive or avoid pregnancy. Typically, you are most fertile on days 11 through 17.

How Birth Control Affects Your Periods

If you take birth control but don’t fully understand how it affects your cycle, you’re not alone. The patch, the ring and birth control pills all work by providing consistent levels of estrogen and progesterone, signaling to the brain that there is no need to stimulate the ovary. Ovary function becomes suppressed, and no egg is released.

In a pill pack, some pills contain no medicine. They’re designed to simply keep you in the habit of taking a pill every day.

Continuous Use Birth Control

Women who want to avoid the days of bleeding can skip those inactive pills and start a new pack. This is known as a continuous-use birth control, and it’s a great option for women who have symptoms – such as heavy bleeding or cramps – during their period that they'd rather avoid.

Women who suffer from endometriosis might also benefit from continuous-use birth control. Endometriosis is believed to be a backflow of menstrual blood into the abdominal cavity. If there is no menstrual blood, there is nothing to perpetuate that process. If you have a diagnosis of endometriosis or think you might be and are interested in exploring birth control as a way to mitigate your symptoms, talk to your gynecologist for more information.