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How birth control works, simply explained.

De werking van anticonceptie, simpel uitgelegd.

How does Birth control work? What methods of contraception are there? And how do they affect your hormones exactly? In this blog, we will tell you more about the hormones involved in your cycle and how contraception works.

We discuss:

The 4 most important fertility 

  • hormones
  • Estrogen
  • Progesterone
  • FSH and LH

Which contraceptive methods are there and how do they work?

  • The Pill
  • The IUD
  • The hormonal IUD
  • The copper IUD
  • Other methods of contraception with hormones
  • Natural contraception

Before we start, let me explain how your menstrual cycle works. Your menstrual cycle can be divided into 2 phases: the phase before your ovulation (follicular phase) and the phase after your ovulation (luteal phase).

Between these two phases, your ovulation takes place. When you are ovulating, you are at your most fertile. 

The 4 most important fertility hormones

There are 4 hormones that play a major role in your fertility:


In the first half of your cycle, the follicular phase, oestrogen has a dominant role. Estrogen causes the lining of the uterus to thicken and thus transforms into an ideal habitat for the fertilised egg. 

As ovulation approaches, you produce more oestrogen which is accompanied by a thin, smooth discharge that is hazy white. This is called the cervical mucus. This sperm-friendly mucus makes it easier for the sperm to swim to the egg and survive longer in the cervix. 


In the second half of your period, so after ovulation, progesterone plays an active role. The amount of oestrogen then decreases and progesterone levels increase.

Progesterone is produced in the ovaries after ovulation. This hormone promotes the implantation of any fertilised egg and also ensures that the endometrium is ready for this. When no fertilisation of the egg occurs, the production of progesterone decreases. As a result, the endometrium is broken down. This is the start of your period.

🔸FSH and LH

Besides the 'well-known' hormones oestrogen and progesterone, there are 2 other hormones that are less known but play a major role in your cycle: follicle-stimulating hormone and luteinizing hormone. 

The follicle-stimulating hormone

The pituitary gland (a gland in the middle of your head, just below the brain, which is responsible for the production of many hormones), produces follicle-stimulating hormone (FSH). The name says it all: this hormone stimulates the follicles - the sacs in which the undeveloped eggs will develop.

In short, this hormone helps your ovaries to prepare your eggs. A number of follicles develop, and after a while one follicle becomes 'dominant'. This is the follicle that grows into an egg, and will make its way to the uterus.

The luteinizing hormone

Luteinising hormone increases after the estrogen level in your body has risen. The increase in luteinising hormone causes the follicle to break open, releasing the mature egg. From the ovary, the egg descends into the fallopian tube. This process is called ovulation. 

Your most fertile days coincide with this LH peak. The peak only lasts one or two days and you can measure these fertile days with an ovulation test. 

Which contraception methods are there and how do they work?

The different methods of contraception each work in their own way. The two best known methods of contraception with hormones are the pill and the hormone IUD. 

In addition, women can also choose a method of contraception without hormones: the copper IUD. 

Finally, we briefly discuss a method that does not involve any hormones or 'instruments': the natural fertility method.

🔹The pill 

The pill is a well-known contraceptive method, where you take a 'pill' every day. The pill releases artificial hormones, which prevent the ova from maturing and suppress ovulation. 

 The artificial hormone used for this is progestogen. It inhibits the release of LH and FSH. And if a woman does not ovulate, there can be no fertilisation. No ovulation also means that your body does not have to 'clean up' the egg cell, which is why you do not really have your period with the pill. 

The monthly bleeding during the stop week of the pill is therefore artificial. During the 6 or 7 days that you stop taking the pill, there is no absorption of artificial hormones and the little endometrium that was built up, will be broken down again. This is called withdrawal bleeding. 

The hormone also causes the lining of the cervix to change. The mucus becomes tough and cloudy and therefore harder for sperm to penetrate.

The negative effects of the pill

The pill is the most widely used contraceptive among women in Belgium. However, the pill does have negative effects which, fortunately, have been receiving more and more attention lately. The pill can reduce your sexual desire (your libido) because you take a form of progesterone every day.

In addition, the pill changes the supply of vitamins and minerals in your body. This can cause all kinds of complaints, such as lethargy or even depression. It is therefore advisable to take supplements that ensure that your vitamins and minerals remain at the right level.

🔹The IUD 

The IUD is a small 'anchor' a few centimetres long that is inserted into you by a doctor or gynaecologist. The IUD is placed once and works for between 5 and 10 years. The IUD prevents the egg from implanting in the uterus.

You can choose between a hormonal IUD or a copper IUD. 

The hormonal IUD 

A hormonal IUD releases the hormone progesterone. This hormone has a particular effect on the endometrium. Sperm cells have greater difficulty in penetrating the mucus of the cervix and a fertilised egg cannot settle in the endometrium. 

Only a small part of the hormones are released into your body. Still, women can have problems with the released hormones (acne, mood swings, bloated feeling, loss of libido).

With the hormone IUD, ovulation sometimes occurs, but the chance of pregnancy is very small: the lining of the uterus is not produced and a fertilised egg cannot implant itself.

Because the IUD constantly releases levonorgestrel (progestogen), ovulation remains suppressed and the chance of pregnancy is very small.

The copper IUD

A copper coil does not contain artificial hormones, which sometimes causes ovulation. A copper coil is a very reliable method of contraception and reduces the risk of pregnancy. The copper IUD works in two ways:

  • Copper is toxic to the male sperm cells. As a result they are not or hardly able to fertilise an egg cell.
  • Copper makes the lining of the uterus unsuitable for implantation of a fertilised egg.

🔹Other methods of contraception with hormones

Besides the pill and the hormonal IUD there are other methods of contraception which use hormones. These include the contraceptive pill, the contraceptive patch, the contraceptive ring and the contraceptive implant. The effect of these methods is the same as that of the pill and hormonal IUD.

🔹Natural contraception

Besides the well-known methods with hormones or an instrument, there are also natural ways to avoid pregnancy. This is also called natural fertility planning. You do not use any medicines and you do not have anything inserted. 

These methods can be used as contraception as well as when wanting to become pregnant.

The best known and most efficient method works in two ways:

  • You measure your basal body temperature.
  • You analyse and check your cervical mucus

Taking your temperature: When you ovulate, your body temperature rises. On average, your temperature after ovulation is approximately 0.2 to 0.3 degrees higher than before ovulation. A rise in your temperature therefore indicates ovulation. 

You measure this increase in the morning with a two-decimal thermometer (your temperature will then be shown as 37.43 instead of 37.4). 

You keep this data in a curve or app. 

Check your cervical mucus:

During your cycle, your mucus secretion changes. The days before ovulation the mucus discharge is increased, thin and clear. During the other days of the cycle, it is sticky and cloudy. 

You can easily recognise the mucus once you know what to look for. 

In addition, you can always double-check when you are most fertile with an ovulation test. This works with urine, in which the luteinising hormone is detected. 

With this contraception method, it is recommended to use reliable methods to monitor your temperature increase. Well-known apps are Natural Cyclus or let yourself be guided by Rebecca from Vrouw & Vruchtbaarheid (Sensiplan Coach). 

We hope this blog has helped you a lot. Do you still have questions? Don't hesitate to contact me! Schedule a call! I am happy to help.