In Vitro Fertilization (IVF)

In Vitro Fertilization (IVF): What It Is & How It Works

Ilustración sobre la fecundación in vitro

What is in vitro fertilization?

In Vitro Fertilization (IVF) is an advanced technique involving the union of the egg with sperm in the laboratory to produce fertilized embryos. These embryos are then transferred to the mother’s womb with the aim of achieving a successful pregnancy. It’s an effective solution for couples facing infertility challenges.


Fertilization of the ovules can be carried out by conventional IVF technique or Intracytoplasmic Sperm Injection (ICSI). It is the technique of assisted reproduction most used in the clinics of Reproductive Medicine but it will be the gynecologist who will determine, after a previous study about the possible causes of infertility, which is the most appropriate for each case.

Discover the different types of IVF and which one is most suitable for your situation.

Types of In Vitro Fertilization

IVF with partner semen

  • Patients in whom simpler previous treatments have failed, such as Artificial Insemination.
  • Women with absence or injury to the tubesnecessary for natural fertilization or Artificial Insemination.
  • Women with advanced endometriosis, with probable repercussions in the tubes and oocyte quality.
  • Situations in which we have a limited number of oocytes or the quality of them is not the most appropriate.

Types of In Vitro Fertilization

IVF with semen of a donor

  • Severe male factor, with poor sperm quality.
  • Previous failure of fecundation with the couple semen
  • Bad embryo quality o failure of repeated implantation in which male factor is suspected as the main cause.
  • Male carriers of a genetic disease that cannot be studied in embryos.
  • Women without a male partner who want to get pregnant.

The IVF process involves several essential steps from ovarian stimulation to embryo transfer. Here, we break down each stage for you.

What is the procedure?

1- Ovarian Stimulation

The ovarian stimulation in IVF or in vitro fertilization consists in the administration of some daily injections that will get the ovaries, instead of producing a single ovule – which is what they do spontaneously every month -, produce more oocytes to obtain a greater number of embryos and, therefore, greater possibility of achieving pregnancy.

Una mujer sosteniendo una jeringa de un tratamiento de fecundación in vitro

The treatment is performed within the clinic and lasts between 10 and 20 days, depending on the protocol used and the speed of response of each patient. During the same, follow-up ultrasounds are performed (between 3 and 4) and the blood estradiol is measured to verify that the growth and evolution of the follicles is adequate throughout the process. The patient must follow the hormone injection schedule at home. It is important to always perform at the same time, that is, if the first stimulation is performed at 9:00 p.m., the rest of the injections are also in that time slot.


Once the follicles and the endometrium of the patient are at the optimum moment, the oocyte puncture is scheduled and prepared.

Un laboratorista realizando un procedimiento de fecundación in vitro

2- Follicular Puncture and laboratory

When it is verified by means of ultrasound that the follicles have reached the appropriate size and it is considered that an adequate number of ovules is already available, the follicular puncture is scheduled around 36 hours after the administration of an hCG hormone injection that induces the oocyte maturation in a similar way to how it takes place in the natural cycle. It is important that the patient does not miss this injection because it is absolutely necessary to perform the Follicular Puncture.

The follicular puncture is performed in the operating room and under sedation, so that the patient does not feel any type of discomfort during the procedure, which lasts approximately 15 minutes.


Once the procedure is finished, the patient returns to the room where she rests a little, dresses and can go home awaiting the call of the Laboratory that will inform her of the result of the extraction and fertilization. Although it is not usual, if after the follicular puncture you felt some discomfort, you can call the clinic to be informed about the steps to follow.


3- Fertilization of ovules

Once we have the ovules (after performing the follicular puncture) and the sperm, (which is normally obtained after the collection of a semen sample by the male), we will proceed to the fertilization of the ovules.


This process can be performed by the technique of conventional in vitro fertilization (IVF), which involves placing an ovule surrounded by sperm in the culture dish or by the ICSI technique, which consists of introducing a live sperm into the ovum by puncturing the same with the help of a pipette.

4- Embryo culture in the laboratory

The resulting embryos after the fertilization of the ovules are observed in the laboratory day after day, and are classified according to their morphology and capacity for division.

Some embryos may become blocked in their development, and will be discarded when considered as non-viable. Once analyzed in quality and development, the best embryos are chosen to transfer to the uterus and wait for implantation and pregnancy.

5- Embryo transfer

The transfer involves the introduction of the best embryos into the womb with the help of a specially designed cannula. The procedure is carried out in the operating room, although in this case it is not necessary to perform sedation, since it is a quick and painless process. After the transfer, the date for the pregnancy test will be informed. During this time, normally about 15 days, it is recommended to continue with your normal activities, as far as possible, not obsess over the result.


6- Embryo freezing

Once the embryo transfer is carried out, the vitrification of the good quality embryos that have not been transferred is carried out in order to be used in a subsequent cycle without the need for a new ovarian stimulation. If the process ends in pregnancy, the remaining vitrified embryos may be used if you wish to have a frozen embryo transfer.

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