You probably already know quite a lot about your menstrual cycle – like how often you get your periods and how heavy they are. In this page we are going to take a more in–depth look at how it all fits together – the menstrual cycle, the ovulation cycle and periods. Obviously, no website can take the place of talking to a healthcare professional, but this should give you a good general understanding of how it all works.
Ovulation is the name of the process that happens once in every menstrual cycle when hormone changes trigger your ovaries to release an egg. This usually happens 12 to 16 days before your next period starts.
- The eggs are contained in your ovaries. During the first part of each menstrual cycle, one of the eggs is being prepared for release from the ovary.
- As you approach ovulation, your body produces increasing amounts of a hormone called estrogen, which causes the lining of your uterus to thicken and helps create a sperm friendly environment.
- These high estrogen levels trigger a sudden increase in another hormone called LH (Luteinizing Hormone). The so–called LH surge causes the release of the egg from the ovary and you‘re ovulating.
- Ovulation normally occurs 24 to 36 hours after the LH surge, which is why LH is a good predictor for peak fertility.
The egg can be fertilized for up to 24 hours after ovulation. If it isn‘t fertilized the lining of the womb is shed and your period begins. This marks the start of the next cycle.
While an egg is only viable for about 24 hours, sperm can remain active for up to five days. It may therefore be surprising to learn that a couple can have intercourse four to five days before the egg is released and still conceive in that cycle.
Menstrual Cycle Start to Finish Explained
Women‘s cycle lengths vary, and the most common cycle length is somewhere between 23 and 35 days. Any variation in cycle length that does occur is more likely to be during the part of the cycle before you ovulate (which is called the follicular phase). Most women then have 12 to 16 days between ovulating and starting their next period (this is called the luteal phase).
The First Day of Your Cycle
The first day of your menstrual cycle is the first day of your period. The period usually then lasts anywhere from 3 to 7 days. You‘ll probably find that if you get any period pains, they‘ll be at their worst on the first day of your period. This is because the hormones in your body are forcing your womb to shed the lining that was built up in the previous cycle.
Preparing for Ovulation
At the beginning of your cycle, your body sends a signal to your brain to start producing follicle–stimulating hormone (FSH), the main hormone involved in producing mature eggs. Follicles are the fluid–filled cavities in your ovaries. Each follicle contains one undeveloped egg. The FSH stimulates a number of follicles to develop and start to produce the hormone estrogen. Your level of estrogen is at its lowest on the first day of your period. From then on, it starts to increase.
Normally one follicle becomes “dominant” and the egg ripens within the follicle as that follicle gets bigger. At the same time, the increasing amount of estrogen in your body makes sure that the lining of your womb is thickening with nutrients and blood. This is so that if you do get pregnant, the fertilised egg will have all the nutrients and support it needs to grow. High estrogen levels are also associated with the appearance of ‘sperm–friendly‘ mucus (or, to give it its technical name, fertile cervical mucus). You may notice this as a thin, slippery discharge that may be cloudy white. Sperm can swim more easily through this mucus and can survive in it for several days.
The level of estrogen in your body is still increasing and it eventually causes a rapid rise in luteinising hormone (often called the ‘LH surge‘). This LH surge gives the ripening egg the final push it needs to fully ripen and be released from the follicle. This process is known as ovulation.
Many women think that they ovulate on day 14, but this isn‘t always the case. Your day of ovulation will vary depending on your cycle length. Some women feel a twinge of pain when they ovulate, but many feel no sensation at all and there‘s no other sign that you are ovulating.
Once the egg (or ovum) has been released, it moves along the Fallopian tube towards your womb. The egg can live for up to 24 hours. Sperm survival is more variable, but typically 3–5 days, so the days leading up to ovulation and the day of ovulation itself are your most fertile – when you are most likely to get pregnant. As soon as you have ovulated, the follicle starts producing another hormone: progesterone.
Progesterone now works to further build up the lining of your womb in preparation for a fertilised egg. Meanwhile, the empty follicle starts to shrink, but carries on producing progesterone, and also starts to produce estrogen. You may get symptoms of pre–menstrual tension (PMS) such as breast tenderness, bloating, lethargy, depression and irritability at this stage.
Preparing for the Next Period
As the empty follicle shrinks, if the egg is not fertilized, levels of estrogen and progesterone decrease because they are no longer needed. Without the high levels of hormones to help maintain it, the thick womb lining that has been built up starts to break down, and your body sheds the lining. This is the start of your period and the beginning of your next cycle.
Or for Pregnancy
If the egg has been fertilized, it may successfully implant itself into the womb lining. This usually takes place about a week after fertilization.
As soon as the fertilized egg has implanted, your body starts producing the pregnancy hormone, human chorionic gonadotrophin (hCG), which will keep the empty follicle active. It continues to produce the hormones estrogen and progesterone to prevent the lining of the womb from being shed, until the placenta (which contains all the nutrients the embryo needs) is mature enough to maintain the pregnancy.
if you‘d like to see an animation of how the menstrual cycle works