Elias Gatos, M.D.
Surgeon Gynecologist – Obstetrician
Scientific Director emBIO Assisted Reproduction Unit

IVF Stages

In vitro fertilisation is a widely used fertilisation technique worldwide effectively resolving a number of current infertility issues. In brief, female ovaries are fertilised under laboratory conditions and then placed in the endometrium. The treatment objective is to achieve pregnancy by transferring one or more embryos to the future mother’s uterus.

When to select this treatment

IVF is mostly used in cases where there is fallopian tube obstruction or dysfunction, hormonal disorders, polycystic ovary syndrome, endometriosis, male reproductive system problems and various other known or unknown infertility causes.

The IVF cycle consists of the following stages:

  • Ovarian suppression and stimulation –drug-induced ovulation

At the initial stage of treatment, ovaries are stimulated by hormonal drugs to produce many ovaries. Should one consider that normally the female body grows and releases only one mature egg monthly, the development of more ovarian follicles is possible by administering hormones (a combination of GnRH and FSH analogues) inducing controlled ovarian stimulation to develop multiple ovarian follicles.

  • Monitoring stimulation with a series of sonograms and hormonal determinations

During ovarian stimulation treatment, the female undergoes systematic sonographic tests to assess whether the ovarian follicles in which eggs are found have achieved the desired size and maturation.

Sonographic and hormonal determination is required to monitor stimulation and administer chorionic gonadotropin (hCG). Ovulation is induced by a midnight injection approximately 36 hours prior to the egg collection and completes the medication in the treatment protocol followed.

  • Egg collection

The egg collection follows (collecting developed eggs); during this process, the gynaecologist performs an ultrasound-guided transvaginal paracentesis of ovarian follicles using precise and fine movements. The ovarian fluid is immediately tested by an embryologist under the microscope to confirm an egg has been collected and the process is repeated for all mature eggs in ovaries. The embryology lab will then let us know of the final number of collected eggs. Egg collection is carried out under intravenous sedation and it is practically a painless and brief process.

  • Sperm collection

Approximately two hours before the egg collection, a sperm sample is collected from the wife’s husband. This samples is subjected to a special activation process, where the most mobile and healthy spermatozoa are selected. They remain in the lab in a nutrient until they are placed with the eggs. In case where no spermatozoa are found in the fluid, a testicular biopsy is performed.

Testicular biopsy (MESA /TESA)

In cases of azoospermia (where there are no spermatozoa at ejaculation), a testicular biopsy is performed to take spermatozoa from the testicle or the epididymis for fertilisation.
There are two ways to collect semen: from the head of the epididymis under local anaesthetic using paracentesis (MESA), or by a small testicular incision or using full sedation and biopsy (TESA). The process is performed by an expert urologist on the same day as the egg collection or one day earlier.

ICSI Microfertilisation

In case of male or unknown infertility suspected to result from the semen’s difficulty to normally enter the egg, ICSI (Intra-Cytoplasmic Sperm Injection) is used. Following the egg collection, microfertilisation is performed using special equipment and a spermatozoon is placed in each egg to be fertilised.

This technique is recommended in cases of semen quality-related issues (reduced number, low mobility, abnormal morphology etc) since it practically overrides almost all male-related infertility issues. Provided that spermatozoa are viable, over 50% of ovaries are normally fertilised, regardless of semen quality. ICSI combined with IVF is currently the most effective method to treat male infertility.


This stage in treatment takes place in laboratories by experienced embryologists. A specific number of spermatozoa is placed with eggs in plates (special tubes) containing a culture nutrient to be fertilised under laboratory conditions, where they will remain for approximately 16-20 hours.

The following morning, eggs are examined using a microscope and it is verified whether or not fertilisation has occurred. The embryologist records the number of eggs normally fertilised and monitors their normal development for the next 2-3 days during which fertilised eggs remain in the lab and continue to grow.

Standard IVF

In standard IVF, eggs are placed in a high concentration of spermatozoa, come in contact with the egg by themselves, and one of them enters the egg and fertilises it. In cases of male infertility, this is the stage where ICSI microfertilisation is applied, i.e. placing a spermatozoon inside the egg using a micropipette (see ICSI microfertilisation).

Embryo transfer

The fourth stage of treatment is embryo transfer, i.e. the transfer of embryos developed in the lab in the uterine cavity. This is a painless procedure performed two or three days after the egg collection or the fifth and sixth day at the blastocyst stage. The embryologist selects the best embryos, which are transferred to the uterine using an ultrasound-guided fine catheter. The number of embryos transferred depends on many factors, but usually two to four embryos are transferred. If there are also other high-quality embryos, they may be cryopreserves. As in normal conception, embryos are implanted in the uterine mucous membrane, the endometrium, by themselves. If there is an implant, there will be a pregnancy. The first pregnancy test is performed approximately 13 days after embryo transfer.

Blastocyte culture

Recently, the development of more ideal culture means resulted in performing the embryo transfer at the blastocyte stage. The term blastocyte refers to a specific stage of embryonic development after 5-6 days of culture. It is essentially the final embryonic development stage prior to its implantation in the endometrium to induce pregnancy. The blastocyte transfer process is similar to the embryo transfer process except it is performed on the 5th or 6th day after the egg process.

This method regards couples who eventually have a number of embryos available for transfer. In these cases, embryon transfer of a few blastocytes (embryos), one or tow, may be carried out to avoid multiple pregnancies without reducing the success rate.

Embryo transfer at the blastocyte stage allows the selection of better-quality embryos (most healthy, morphologically intact, and most developed embryos) since only genetically healthy and potentially capable of implantation embryos will reach this stage (20-40%). Moreover, it mimics the normal reproductive process and offers a better synchronisation of embryos-endometrium.

If the amount of embryos to survive this stage is zero, embryo transfer may not take place.


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