The menstrual cycle is something that lots of people go through each month, however, many of the phases within the cycle can’t be seen or felt because they don’t necessarily result in physical symptoms. This can make it difficult to track where you are in your cycle, and how long it is.
The overall cycle is calculated from the first day of your period to the day before your next period starts . Every cycle, however, is split into four main phases: the menstrual phase, the follicular phase, the ovulation phase and the luteal phase. During each of these phases, various changes are happening in your body, either preparing your body for a baby or getting ready for a period. Each phase differs in length and some overlap with each other.
What are the four stages of the menstrual cycle?
Below, you can find more information about each of the four menstrual cycle stages, including what is happening in your body at this time and how long each phase lasts on average.
This is the first stage of the menstrual cycle and begins when an egg hasn’t been fertilised by a sperm previously in the cycle. Oestrogen and progesterone levels drop and the already thick uterine lining begins to shed because an embryo hasn’t implanted. This is what’s commonly known as a period. As well as bleeding, you may also experience cramps, mood swings, bloating, tiredness and headaches.
Menstruation can last anywhere from three to seven days , but you’ll likely know what is ‘normal’ for you. Five days tends to be the average.
The follicular phase also starts on the first day of your period, so it does overlap with the menstrual phase. Towards the last couple of days of your period, the follicle stimulating hormone (FSH) begins to rise and your basal body temperature (BBT) drops slightly.
FSH is important because it’s responsible for the release of eggs from the ovaries. During the follicular phase, FSH stimulates the ovaries to produce a number of ovarian follicles (usually around five to 20). These follicles are small sacs that contain an immature egg. One of these eggs will outgrow the others and mature more quickly, ready to be released from the ovary during ovulation (in some cases, more than one egg can mature, which is when twins can be conceived). The remaining follicles containing immature eggs will be reabsorbed into the body.
While the menstrual phase lasts up to seven days, the follicular phase takes you through to just before you ovulate, which is typically 14 to 16 days after the first day of your period.
At the end of this follicular phase, before ovulation (approximately 34 to 36 hours before ), there is a surge in luteinising hormone (LH). This surge shows that the mature egg is about to be released by the ovary and enter the fallopian tubes. It is LH that many ovulation tests are looking for , and can show couples when they should have sexual intercourse for maximum chances of conception.
The ovulation phase is the one where the mature egg is released. This is the peak window for achieving pregnancy. When you’re on a contraceptive pill, particularly one that contains desogestrel, ovulation can be inhibited in up to 99% of cases when you take your pill at the same time each day, so your ovaries don’t release any eggs. This is why they’re effective at protecting against unwanted pregnancy.
However, when ovulation does occur, the egg travels down the fallopian tube where it can be fertilised by sperm. Signs that you’re ovulating include an increased BBT and thicker vaginal discharge that can have a similar texture to egg whites.
Whereas LH increases during the follicular phase, it decreases again once the egg has been released. If an egg isn’t fertilised, it will die within 24 hours.
During the luteal phase, your body either prepares you for pregnancy or a period. The ovarian follicle that released the mature egg becomes what’s known as the corpus luteum. This is an organ that releases progesterone and is primarily there to prepare and thicken the endometrial layer of the uterus, ready for an embryo to implant.
However, unless a pregnancy results in increased human chorionic gonadotropin levels (hCG), the corpus luteum begins to die after around nine to 11 days . Once the corpus luteum has been reabsorbed, the levels of progesterone and oestrogen drop and this causes the start of the menstrual cycle. It’s during this time that some women can begin to experience premenstrual syndrome (PMS) symptoms, including mood swings, headaches, food cravings, bloating and breast tenderness.
This phase is usually 14 days long and lasts from when ovulation occurs (at approximately day 14) to the end of the cycle, when the body will get ready to start the process again.
How long is a menstrual cycle?
The average menstrual cycle is 28 days, and most cycles are approximately 25 to 30 days. Some women, however, may have longer or shorter cycles than this, which is also completely normal.
As mentioned previously, the period itself will generally last anywhere from three to seven days. The follicular phase lasts from the first day of your period to ovulation, around 14 days though for some women this could also be anywhere from 11 to 27 days. Ovulation occurs, which usually lasts around a day, and the remainder of the cycle is the luteal phase, lasting for around 11 to 17 days.
According to these time frames, some women can have a menstrual cycle that lasts from as little as 22 days to as long as 44 days. You’ll likely know what is normal for you.
There are some things that can affect the length of your cycle, including hormonal contraceptives.
Why does a menstrual cycle get shorter or longer?
Menstrual cycles don’t usually operate like clockwork, and irregular periods are very common. They may come at the same time each month, or it may differ by a few days. One period might last four days and another one could last seven, for example. This is very normal and not usually anything to worry about.
However, if you’re concerned or wondering why this is the case, there are some things that can impact your cycle.
Being on hormonal birth control can affect your periods, typically making them shorter and lighter. Some women who take a progestogen-only pill (POP) that contains desogestrel might not get periods at all because they don’t ovulate.
Other things that could make your cycle shorter or longer include:
- Polycystic ovary syndrome (PCOS) - this condition prevents the follicle sacs from releasing the immature eggs, so women might not ovulate as often or at all
- Weight loss or gain
- Extreme exercise