Pre-gestational testing PGS/PGD

This process is extremely precise and requires a huge embryological experience. In a very simplified way, it can be described as taking some cells from an outside part of a blastocyst on the fifth day of culture. Embryos are then frozen, and after the analysis, unaffected ones can be transferred.

Pre-gestational screening is genetic screening, which detects chromosomal abnormalities before an embryo is transferred to the uterus. It requires an IVF procedure.

The chromosomal anomalies of embryos are one of the main reasons for IVF failure. Each cell of an embryo should contain 46 (23 pairs) chromosomes. They carry genes- contain information in what way an embryo would grow and become a healthy child. An abnormal number of chromosomes is called “an aneuploidy.” Aneuploid embryos do not usually implant in the uterus at all. If they do so, a pregnancy ends in miscarriage. However, few aneuploidies allow pregnancy to develop rather normally. The most common chromosomal anomaly is trisomy of the 21st chromosome – Down’s syndrome.

PGS  is recommended in case of:

• recurrent implantation failures
• recurrent miscarriages
• advanced maternal age (above 37)
• an abnormal karyotype of one of the prospective parents – after genetic consultation
• a previous child born with trisomy
• other factors leading to a high risk of a trisomy

Preimplantation testing is a direct test to detect a specific mutation (in the case of monogenic diseases) or a rearrangement of genetic material in chromosomes (translocation). PGD is used in a family occurrence of a genetic disease. Thanks to PGD, even people with a genetic disorder have a chance for healthy offspring. A genetic consultation must precede PGT.

The most common monogenic disorders include:

• cystic fibrosis,
• Huntington’s disease,
• Spinal muscular atrophy (SMA),
• tuberous sclerosis,
• sickle cell anemia,
• hearing loss.

In a situation where parents are carriers of genetic abnormality, their chance of having healthy offspring is reduced. PGD allows checking the embryos for a specific mutation and transferring embryos without it. Also, it allows screening embryos for chromosomal anomalies like trisomies and rearrangements. In such cases, even couples who do not have fertility issues decide to use the IVF-PGD or IVM (In Vitro Maturation).

In the IVM, maturation of oocytes takes place outside the female body – in a laboratory. IVM is used in women, for whom hormonal stimulation could be dangerous, and there could be a risk of overstimulation. The preparation for the IVM procedure consists of the cycle monitoring:  serial US scan to measure growing ovarian follicles and blood tests to check the estradiol levels. However, not all menstrual cycles are appropriate to carry out the oocyte pick-up for IVM. Unmatured oocytes are aspirated, and they grow and mature in the lab. They can not be fertilized before a set of complicated laboratory treatments. They are put in special media to grow and develop. After maturity assessment, they are fertilized by the ICSI. The next stages of the treatment are similar to a typical IVF.