Understanding Your Menstrual Cycle

2023-06-29T12:02:02-06:00August 23rd, 2021|

Written by: Dr. Wael Salem, a board certified reproductive endocrinology and infertility specialist at CCRM Fertility of San Francisco

Whether you’re trying to get pregnant or want to prevent pregnancy, understanding your menstrual cycle will help to better guide your decisions.

The 4 Phases of the Menstrual Cycle

Your menstrual cycle can be broken down into four distinct phases:


Menstruation, or getting your period, is when blood and tissue are shed from your uterine lining (known as the endometrium) through your vagina.

Follicular Phase

On the first day of your period, the follicular phase of your menstrual cycle begins. There can be variations in how long this phase lasts, meaning how long it takes to develop an egg and ovulate. During the follicular phase, your brain signals the pituitary gland to release follicle-stimulating hormone (FSH) to encourage the ovary to produce around 5-20 fluid filled sacs (follicles) which each contain an immature egg. Typically, one dominant egg will mature while the remaining follicles are reabsorbed into the ovary. The growing follicles work to grow the endometrium in preparation for a potential pregnancy to implant.


Next, a surge of luteinizing hormone (LH) triggers ovulation and releases the mature egg into the fallopian tube where it will travel to the uterus. If you’re trying to get pregnant with ovulation predictor kits (OPKs), this surge of LH gives you a positive test and is when you would want to try timed intercourse. The egg only has the capacity to be fertilized for about 24 hours from the time of ovulation.

Luteal Phase

The luteal phase is the second half of your cycle after ovulation. The ovarian hormones estrogen and progesterone will be elevated to support a potential pregnancy.  If an embryo does not implant and a pregnancy is not achieved, the progesterone and estrogen will naturally decrease at the end of this phase and your period will start.

How long is the average menstrual cycle?

The length of your cycle is the number of days from the first day of one period to the first day of your next period. The average menstrual cycle ranges from 21 to 35 days, although this can vary from person to person and one cycle to the next. If your period is irregular or if the length is shorter or longer it can indicate an underlying ovulatory disorder.

A typical menstrual period can be anywhere from 3 to 7 days, and on the heaviest flow day, it’s normal to change a pad or tampon five or six times. Your provider or fertility specialist will want to know your cycle lengths to determine if there may be some underlying issue leading to infertility.

It’s important to understand the timing of your cycle and the variation in that timing. If you have a shorter cycle, you may ovulate earlier than on day 14 of a typical 28-day cycle.

When should you be concerned?

Your menstrual cycle is known as the fifth vital sign. Much like your pulse and blood pressure tell you about your heart and circulatory system, your menstrual cycle indicates what’s going on with your reproductive system—inside your ovaries, fallopian tubes, and uterus. There are times when it’s important to address concerns with your provider or fertility specialist.

While you could see some brown spotting before your period starts, spotting or having bright red bleeding in the middle of your cycle should be addressed with your doctor. If you are bleeding longer than 7 days, your cycle length starts getting longer, or if you’re skipping periods and aren’t on hormone birth control, you should let your doctor know.

If you have irregular periods or have concerns about your menstrual cycle and would like to get pregnant, contact us to make an appointment with a CCRM Fertility specialist.

About CCRM

CCRM is one of the industry's leading pioneers in fertility science, research and advancement, offering access to a national network of award-winning physicians, a full suite of fertility services, innovative technology and cutting-edge labs.

Book your appointment Call