The menstrual cycle is a complex biological process between various glands and organs. The process starts in the brain, where the hypothalamus causes the pituitary gland to produce specific chemicals which in turn triggers the ovaries to produce the sex hormones estrogen and progesterone. The entire cycle takes on average 28 to 29 days but that can vary between person and cycle (it can be as short as 24 days or as long as 38), and can change with age. The length of the cycle is counted from the first day of menstruation, or period, and ends on the last day before the next period starts.
The four main phases of the menstrual cycle are:
Duration: Average length is 5 days but can last between 3 to 8 days depending on your cycle.
Menstrual fluid contains blood, endometrial cells and mucus. Pad, tampons, sponges, cups, or period panties can be used to absorb or capture this fluid. These need to be changed or cleaned out frequently. Note the usage of tampons can be associated with an increased risk of a rare illness called Toxic Shock Syndrome (TSS, see below).
Duration: Average length is 16 days but can last anywhere from 11 to 27 days depending on your cycle.
This phase begins on the first day of the period and ends on the day of ovulation. The process starts when the pituitary gland releases the follicle stimulating hormone (FSH) which causes the ovaries to create between 5 to 20 follicles (tiny cysts or nodules) on their surface. Each one of these follicles contains an immature egg cell. In most cases only one of the egg cells will mature into an egg which will be released during ovulation (usually around day 10), the remaining cells will die. The follicles’ growth stimulates the uterine lining to thicken in preparation for a possible pregnancy, and the developing follicles raise the level of estrogen in the body which causes the hypothalamus in the brain to react and releases gonadotrophin-releasing hormone (GnRH). This hormone then causes the pituitary gland to produce raised levels of luteinizing hormone (LH) and FSH which then leads to ovulation.
Duration: 24 Hours
Ovulation is the moment a mature egg cell is released from the surface of an ovary and typically occurs about mid-cycle (i.e. around two weeks before the beginning of menstruation). The high levels of LH produced by the pituitary gland trigger ovulation, typically within two days. The egg is funneled through the fallopian tube and toward the uterus by waves of small, hair-like projections.
The life span of a typical egg is only around 24 hours. If it does not meet a sperm cell during this time, it will die.
Even though ovulation technically only lasts for 24 hours, pregnancy is possible during the six days leading up to and including ovulation since the life span of sperm inside the vagina/uterus is three to five days - some studies claim as high as seven. The likelihood of pregnancy is increased significantly if intercourse happens in the three days leading up to and including the day of ovulation (sometimes referred to as the “fertile window”). That means for a person with a regular 28-day cycle, the most fertile days are days 12 to 14.
Duration: Average is between 12 to 14 days, however it can be anywhere from 8 to 16 days depending on your cycle
During ovulation the follicle releases the egg. The now ruptured follicle remains on the surface of the ovary and transforms into a structure called “corpus luteum”. The Corpus Luteum releases progesterone and small amounts of estrogen. These hormones cause the uterus to maintain the endometrium so that a fertilized egg can implant (or stick).
If a fertilized egg implants itself into the lining of the uterus, it will produce hormones that maintain the corpus luteum. One of these hormones is human chorionic gonadotrophin (HCG), which is the hormone detected in urine-based pregnancy tests. The corpus luteum then keeps producing the raised levels of progesterone so that the thickened lining of the uterus is maintained and pregnancy can progress. If there is no pregnancy, the corpus luteum withers and eventually dies (usually around day 22). The resulting drop in progesterone then causes the lining of the uterus to fall away, starting the menstrual cycle anew.
Tracking the menstrual cycle
It is beneficial to track the menstrual cycle for these reasons:
- If periods are regular, tracking them will help with knowing when to expect ovulation and the fertile window and when to expect the next period.
- If periods are not regular, or there is heavy bleeding or pain, tracking can help identify symptoms and can help sharing them with your health provider and identify possible issues.
Tracking can be as simple as marking dates on a calendar or as involved as using dedicated apps or diaries.
Common menstrual problems
Some of the more common problems associated with the menstrual cycle include
PMS – Pre-Menstrual Syndrome
Hormonal changes and events immediately preceding a period which can trigger a range of side effects including fluid retention, headaches, fatigue and irritability. Treatment options include exercise and dietary changes.
Dysmennorrhoea - Painful periods
This occurs when the uterus is prompted by certain hormones to squeeze harder than necessary to dislodge the lining. Treatment options for painful cramping can include pain-relieving medication and the oral contraceptive pill.
Menorrhagia - Heavy Bleeding
The amount of blood lost during a cycle differs from person to person, can change from cycle to cycle, and changes with age. But sometimes bleeding can become very severe (especially during perimenopause, see below), which can cause severe blood loss and anemia. If this is a common occurrence you can use oral contraceptives or hormonal intrauterine devices (IUDs) to regulate the flow.
Amenorrhoea - The absence of one or multiple menstrual periods.
It is normal during pre-puberty, pregnancy, lactation and post menopause to not have a period. At all other times it is considered abnormal and can be a sign for health issues. There is a range of causes (lifestyle factors, stress, medications, and hormonal imbalances to name a few) and so treatment is dependent on identifying the correct cause.
Onset of the First period
The average age for a person to get their first period in the United States is 12 years old, but not everyone starts at the same age. Your period can start any time between 8 and 15 years old. The first period typically starts roughly two years after breasts first start to develop and pubic hair begins to grow. The age at which a person’s parent started their period can help predict when a person may start their own period. You should consult a doctor if there is a period before the age of 8, if there is no period by age 15 or there is no period three years after breast growth.
On average, people have a period for about 40 years of their life until perimenopause begins, which is the time when the body begins the change to menopause. Perimenopause may take a few years, during which menstruation may not come regularly. Doctors consider the body to be in menopause after the absence of a period for 12 months. This usually happens between the ages of 45 and 55. The average age of the onset of menopause in the United States is 52.
Periods also stop during pregnancy and may not come back right away while breastfeeding. While there are multiple causes that can result in a missed period (as discussed above), if at any time you don’t have a period for 90 days (three months), and you are not pregnant or breastfeeding, there may be underlying issues and you will want to check with a doctor or nurse. Your doctor will check for pregnancy or any health problems that can cause periods to stop or become irregular.
How often should I change my pad, tampon, menstrual cup, sponge, or period panties?
Make sure to follow the instructions that came with your period product. Best practice is to try to change or rinse your feminine hygiene product before it becomes soaked through or full.
Pads – change every few hours
Tampons - should not ever be worn for more than 8 hours because of the risk of toxic shock syndrome (TSS)
Menstrual cups and sponges may only need to be rinsed once or twice a day.
Shop our menstrual cups here
Period panties (specially designed underwear with washable menstrual pads sewn in) can often last a full day but that depends on design/style and amount of flow.
Make sure to use a product that is appropriate in size and absorbency for the amount of menstrual bleeding. The amount of menstrual blood usually changes during the different days of a period. It is not uncommon to use different products on different days of the period, depending on how heavy or light the bleeding is.
Toxic Shock Syndrome (TSS)
Toxic shock syndrome is a rare but sometimes deadly condition. It can happen when tiny abrasions in the vagina are invaded by staphylococcus or streptococcus bacteria. You can be at risk for TSS if you use more absorbent tampons than you need for your bleeding or if you do not change your tampon often enough (at least every four to eight hours). Menstrual cups, cervical caps, sponges, or diaphragms (anything inserted into your vagina) can also potentially increase the risk for TSS if they are left in place for too long (usually over 24 hours).
It is also possible to get TSS even if you are not menstruating. Today, most cases of TSS are caused by having cuts and burns on the skin, recent surgery or certain viral infections (chicken pox or flu). The reason we most associate TSS with tampons is because of a case in 1980 in which 63 women died of the infection. This was associated with a new brand of super absorbency tampons which were promptly taken off the market.
Best practices to avoid getting TSS: Change out your tampon every 4-8 hours, make sure to use the correct absorbency for your flow, and always wash your hands before handling your tampon. If you are using a menstrual cup, make sure to wash your hands before inserting the cup, don’t leave the cup in longer than 12 hours, and sanitize the cup between every cycle.
If you experience any symptoms of TSS, remove the tampon, menstrual cup, sponge, or diaphragm, and call 911 or go to the hospital right away. TSS can progress extremely quickly and is very dangerous.
Symptoms of TSS include:
- Sudden high fever
- Muscle aches
- Kidney or other organ failure
Corpus Luteum: a gland produced by an egg follicle that produces hormones to ensure pregnancy can occur.
Estrogen: A female sex hormone that prepares the uterus for pregnancy, and develops and maintains secondary female sex characteristics.
Fallopian Tube: A pair of long slender tubes that transport the egg to the uterus.
Follicle: (also known as the Graafian follicle) The small ovarian sacs containing the immature ovum, or egg.
Genitalia: The organs of reproduction, especially the external organs.
Hypothalamus: A region of the brain that regulates the releasing of hormones by the pituitary gland.
Ovary: (plural: Ovaries) A female reproductive gland which develops eggs and certain hormones. Normally two are present, and they are located at the end of each fallopian tube.
Pituitary Gland: A small gland at the base of your brain which regulates hormones.
Progesterone: A hormone that prepares the uterus to receive a fertilized egg for pregnancy.
Uterus: Also known as the womb. The muscular organ in which pregnancy occurs.
Vulva: The external female genitalia.