All content within this page has been reviewed and endorsed by
Dr Tariq Miskry, Consultant Gynaecologist & Obstetrician
Your menstrual cycle occurs each month when your reproductive system goes through numerous hormone-driven changes. During each cycle, an egg develops and is released from the ovaries. The lining of the uterus builds up to support a possible conception. If a pregnancy doesn’t occur, the uterine lining sheds during a menstrual period, and then the cycle starts again.
There are four parts, or phases, that repeat during each cycle, which unfolds over 21 to 35 days. Here’s what you need to know about each one, and the menstrual cycle problems that can accompany them.
The menstrual phase (menstruation)
The menstrual cycle phase is the part commonly referred to as 'your period'. The official start of your cycle is the first day of your menstrual phase – the first day of your period.You may be thinking, 'Where is this stuff coming from?' Menstrual blood is shed from the lining of your uterus. It goes from your uterus through your cervix and vagina and then out through your vaginal opening.Menstruation usually lasts about three to seven days. It may seem like more, but the average amount of menstrual flow for your entire period is about 35 ml! Generally, you may experience discomfort as your uterus contracts to shed its lining. Some women also find that hormonal changes related to menstruation cause their breasts to ache or make moods, acne or migraines more severe. Usually these symptoms can be treated with over-the-counter anti-inflammatory medication or a heating pad.
The follicular phase
This stage of the menstrual cycle is all about your body preparing for pregnancy each month. It starts with your oestrogen hormone telling the lining of your uterus to thicken and develop to prepare for a fertilised egg. At the same time, another hormone, known as the follicle-stimulating hormone (FSH), stimulates your ovarian follicles to grow. Each follicle contains an egg. Usually, one egg will get totally ready for fertilisation each month. Your oestrogen levels rise dramatically during the days before ovulation and peak about one day before the next phase starts.
The ovulation phase
During this phase, a surge in oestrogen triggers a spike in a third hormone – the luteinising hormone, or LH. LH is what makes a follicle rupture and release an egg. If you have a regular 28-day menstrual cycle, the ovulation stage of the menstrual cycle will usually occur on Day 14. However, most women have different menstrual cycle lengths. In general, ovulation happens 11 to 16 days before your upcoming period.Ovulation is what it’s called when one of the ovaries releases a mature egg. The egg travels out of the ovary, into the nearest fallopian tube, and then into your uterus. As the egg moves down the fallopian tube over the course of several days, the lining of the uterus continues to grow thicker and thicker. It takes about three to four days for the egg to travel toward the uterus. From there, an egg will wait for about 24 hours in the hope of being fertilised before it starts to degenerate.
The luteal phase
After ovulation, the luteal stage of the menstrual cycle begins. The empty follicle turns into a corpus luteum. The cells of the corpus luteum produce oestrogen and large amounts of progesterone. Progesterone stimulates your uterine lining to prepare for a fertilised egg. Here’s where two things can happen. If you become pregnant, the egg moves into your uterus and attaches itself to the lining. If you are not pregnant, the lining of the uterus is shed through the vaginal opening. Your period starts and a new menstrual cycle begins. During this phase, many women face pre-menstrual syndrome, precipitated by mood swings caused by a drop in oestrogen and progesterone. Other symptoms include cravings, fatigue, increased anxiety or depression.
If your cycle changes from month to month by more than 20 days, if your regular periods go awry, or if your cycle is shorter than 24 days or longer than 38 days you should call a doctor.
Heavy bleeding makes periods more painful and more likely to disrupt your day-to-day activities. However, they are also a sign that your body is producing and releasing a lot of life-giving blood.
You should speak to your doctor if:
If you have missed three periods in a row, or have not started menstruating by age 15, you may have a condition called amenorrhoea. You should see a doctor if your breasts have not started developing by age 13 or if your period has not begun three years after breast growth.
Possible causes of a missed period are:
If you are concerned, make an appointment to see your doctor.
You should see your doctor if:
Your doctor will begin to diagnose you by looking at the most common likely cause for your age group.
These painful headaches can be caused by your period, possibly due to hormonal changes.