Laboratory stage of the IVF treatment



Conventional IVF

This represents the main laboratory stage of your attempt. A few hours following the egg collection the embryologist places a specific number of motile spermatozoa in the culture dishes containing the eggs.

In conventional IVF there is no further intervention.

The spermatozoa approach the egg on their own and one of them penetrates it and fertilises it.



Intracytoplasmic sperm injection (ICSI)

ICSI is applied when the sperm is incapable of fertilising the egg on its own (as previously described). Using highly specialised equipment, the embryologist deposits a single spermatozoon inside the egg to induce activation and fertilisation of the egg. Only one motile spermatozoon is required for each egg.

The method has been successfully used since 1992 and overcomes almost all the barriers that cause male infertility.

Thanks to ICSI, men with severely compromised sperm quality (reduced number, low motility, bad morphology or ejaculation problems) can now father a child of their own; something that was impossible in the not so distant past.

Until today, thousands of babies have been born from ICSI, with no indication that the method presents a danger for embryo quality and child health (recent large scale epidemiological study from Belgium).

Except the way that fertilization occurs, the procedure is the same as conventional IVF as far as the man and woman are concerned.



Fertilization check

The fertilization check is performed the following morning, i.e. after culturing the eggs and sperm together for 16-20 hours. The embryologist checks how many eggs have been fertilized normally using a microscope, while he segregates abnormally fertilized eggs (e.g. polyspermy). Polyspermic eggs (eggs that have been fertilized by more than one spermatozoa) should not be transferred to the uterus as they are suspected to cause pathological pregnancies (miscarriages, moles). Normally fertilized oocytes are placed are cultured and continue to develop. Their normal development is monitored during their culture in the laboratory (usually 2-3 days).



Assessment of embryos

Successful pregnancy largely depends on the number and quality of the embryos transferred to the uterus. Therefore, it is necessary to classify the embryos as they develop and to select for transfer those that fulfil most qualitative criteria.

The assessment and selection of embryos is based on two main criteria: the division of embryos into more cells (blastomeres) and morphological appearance of the blastomeres.

Division: The second day after egg collection the embryos should have divided into 2-4 cells. 4-cell embryos are judged to be superior to 2-cell embryos, which seem to develop in a slower rate. On the third day, the embryos should have reached a stage of 5-8 cells, with 8-cells being better than 5-cell embryos.

Morphology: At Eugonia, we classify the embryos into 4 categories, from I to IV. The best score is I and it describes embryos without fragmentation and regular blastomere shape (round or oval). Category IV includes embryos with high fragmentation, which display a significantly lower implantation potential. Therefore, the ideal embryos should be 4-cell grade I-II embryos for transfer on day 2, and 8-cell grade I-II embryos for transfer on day 3.



Blastocyst transfer

The term blastocyst describes a certain stage of embryo development, after 5-6 days of culture. The Blastocyst contains 60-120 cells that from two distinct groups. The outer cell mass (trophoblast) that will give rise to the placenta, and the inner cell mass that will form the embryo.

The procedure of blastocyst transfer is similar to the embryo transfer on days 2 or 3, as described later.



Why blastocyst transfer is not recommended as a routine method

Only a few embryos reach the blastocyst stage under culture conditions. According to international studies, this percentage is estimated to be around 20-40% of fertilised eggs. This may be due to either the varying developmental potential of the embryos, or to suboptimal culture conditions that fail to fully support the increased metabolic requirements of a 60-120 cell embryo (blastocyst), while sufficiently covering the needs of 2-8 cell embryos.

Therefore, we cannot identify with certainty the reasons why an embryo has not reached the blastocyst stage, as these may be due to reduced developmental competence or suboptimal culture conditions. This is why the application of blastocyst transfer has a limited scope in routine ART programs.

At Eugonia, we run a successful program of blastocyst culture and transfer, following certain indications, according to international criteria. The scientific team of Eugonia has the necessary knowledge and experience to inform you and suggest possible ways forward.



Assisted hatching

During natural conception, the blastocyst hatches from the embryonic shell, the zona pellucida, on the 5th or 6th day after fertilization. The fully hatched blastocyst is the last free-form embryonic stage and the only stage when the embryo has the capacity to attach and implant in the endometrium. However, in some cases, the zona pellucida is harder or thicker than normal, obstructing the process of hatching and, as a result, impairing successful implantation.

When the embryos develop in culture, there is another possible intervention before the embryo transfer; the embryologist can assist blastocyst hatching by opening a small hole on the zona pellucida (assisted hatching), using either a special laser device or a chemical solution.

The initial excitement over the usefulness of assisted hatching in implantation has not been widely accepted by embryologists. The method does not seem to significantly increase implantation rates, while it subjects the embryos to further stress. However, assisted hatching has been proven to slightly improve implantation in special cases, such as thick zona, frozen-thawed embryos, eggs from women of increased age, etc.



Preimplantation genetic diagnosis (PGD)

PGD allows the identifications of genetic abnormalities of the embryo while it develops in culture. The method detects certain numerical or structural chromosomal abnormalities in the embryo, which are responsible for known congenital or hereditary diseases.

The abnormal embryos are therefore identified and excluded from the embryo transfer. Only healthy embryos are selected for transfer in the uterus. If the gene causing a genetic disease is located on a sex chromosome, then sex selection is required to avoid development of the disease in the embryo.

This is the only case when embryo selection is performed. Cases that require PGD include -thalassaemia, cystic fibrosis, Down syndrome, etc. PGD has an advantage over conventional prenatal diagnosis methods, ie amnioparacentisis and trophoblast biopsy, as it can avoid potential abortion if the diagnosis is positive for a certain abnormality.

It must be clear that PGD searches for specific abnormalities and does not preclude the birth of a child with a different genetic disease.

Also, PGD can help explore the reasons for repeated implantation failure, by identifying aberrations in the genes that signal programmed cell death (apoptosis).

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