What is IUI (intrauterine insemination)?

IUI stands for Intrauterine Insemination. During an IUI, the sperm is introduced directly into the uterus through a tube to shorten the path to the eggs. This increases the chance of fertilization of an egg. To increase this chance even further, the quality of the sperm is first increased by pre-processing it in a laboratory. On the day of the IUI, the man must produce his sperm in a clinical environment, i.e. in a special room of the hospital. This is inserted after pre-processing.

Who is IUI intended for?

IUI is a treatment that is used when there is reduced fertility. The condition is that there are no major abnormalities in the sperm, in terms of number, motility and shape of the sperm cells. The woman’s fallopian tubes must also be easily accessible. IUI can be a good treatment in the following cases:

  • If no clear causes have been found for reduced fertility in either partner.
  • If the woman has a mild form of endometriosis.
  • With ‘hostile’ cervical mucus or too little mucus, which makes it difficult for the sperm cells to pass through the cervix.
  • In case of ovulation disorders, for example if insufficient eggs are released.
  • In case of reduced male fertility, where there must be at least 3 million motile sperm cells after pre-processing.
  • When the man produces antibodies against his own sperm cells, causing them to become stuck together and no longer able to move. These antibodies can be partly removed during the preprocessing of the sperm.


IUI with or without hormone treatment

IUI can be applied with or without hormone treatment. Without hormone treatment, this means that the woman’s natural cycle is followed.

IUI in the natural cycle

When IUI is used in the natural cycle, the woman must determine when ovulation takes place by means of daily urine tests or blood tests. The IUI is then done around the time of ovulation. IUI in the natural cycle is mainly used in the case of problems with the cervical mucus, if the man produces antibodies against his sperm and/or when the man has a low number of motile sperm cells.

IUI with hormone treatment

In other cases, IUI is usually combined with hormone preparations. The woman is then given hormone preparations (gonadotrophins) every day to develop two to three egg sacs. Tablets are sometimes used for this, but the use of injections has proven to be more effective. Once the egg has matured sufficiently, an injection is administered to induce ovulation. Ovulation usually takes place 36-40 hours after the injection and the IUI then takes place on the day of expected ovulation. During treatment with hormone preparations, regular checks are made to see how the ovaries respond to the stimulation. Because multiple egg sacs are developed, there is an increased risk of multiple births, which can entail increased risks. If during the check-up it appears that more than three egg sacs are developing, the treatment is generally stopped. The checks are done by blood tests and/or ultrasound.

Risks of the treatment

In general, there are few risks associated with IUI. Sometimes treatment is (temporarily) stopped because the risk of multiple births becomes too great due to the development of more than three egg sacs. With a multiple pregnancy there is a greater risk of miscarriage or the birth of babies with a lower birth weight. This risk is limited by starting with a low dose of hormone preparation and gradually increasing it. This in combination with the checks during treatment makes the chance of multiple births less than ten percent. A rare condition that can occur is OHSS (ovarian hyperstimulation syndrome). The ovaries then swell considerably because too many egg sacs grow. This then causes abdominal pain and fluid accumulation in the abdominal cavity. If this occurs, treatment is interrupted.

Success rate of the treatment

The success rate of IUI combined with hormone preparations is fifteen percent per cycle. With reduced male fertility this is around ten percent. After six treatments the chance of pregnancy is around fifty percent.
If IUI has not resulted in a pregnancy after six attempts, another treatment is generally recommended, such as IVF or ICSI.

Why not IVF straight away?

The aim of the treatment is always to achieve the pregnancy in the most natural way possible. If nature needs to be given a helping hand, the first choice, where possible, lies with IUI. This is because IUI takes place in the woman’s own body. Furthermore, the chance of success with IUI is greater if the woman has a low egg reserve. Because fewer eggs can be harvested, IVF has a lower success rate.

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