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Preimplantation Diagnosis

Preimplantation genetic screening

During the blastocyst stage (5 days after development outside the womb), cells differ and have multiple functions: actual embryo and the placenta. Some cells from the «placenta» (trophoblast) are extracted and examined 5 days after fertilization in order to determine if all 23 chromosome-pairs are present in their correct form. This is the process of genetic examination in which the chromosomally healthy embryos are selected. Chromosomally healthy embryos are ideal, as they have a higher chance of implantation and thus to the birth of a healthy child. 

What is PGS?

Depending on the woman’s age, an abnormal number of chromosomes is detected in 25%-80% of all embryos which develop into blastocysts. This cannot be observed with a microscope. In Switzerland, as of 1.9.2017, it is possible to examine the chromosomes of individual embryos through preimplantation genetic screening (PGS=PIGS). Thereby it is possible to select embryos with 46 chromosomes in the correct form for the embryo transfer. The preimplantation genetic screening is extremely beneficial, as the selection of chromosomally healthy embryos increases the likelihood of pregnancy per embryo inserted into the uterus, as well as decreasing the risk of miscarriage.

How is PGS carried out?

3-5 placenta cells are extracted 5 days after fertilization and examined for their chromosome content. At the earliest in the following month, the embryo/s containing 46 chromosomes are inserted into the uterus.

What is the situation in Switzerland?

On the 1st of September 2017 one of the most progressive reproductive-medicinal laws of the world came into effect: up to a maximum of 12 fertilized eggs can be developed into embryos and examined for chromosomes. Because of this, the probability of pregnancy per embryo transfer is increased and the risk of a miscarriage reduced.

Who is best suited for PGS?

We expect that PGS is suitable for about 20% of all couples, and that about half of these couples choose PGS. Younger women with functionally good ovaries have mostly maximum few benefits with this test. The PGS is very well suited for women aged 40 years old or above with many blastocysts, given that with PGS, only embryos with a correct number of chromosomes will be inserted into the uterus and thus significantly increasing the success chance per transfer. PGS is also recommended for selected patients who have gone through a high number of pregnancy losses (abortions), particularly if the patient has a desire for children.

We also suggest carrying out PGS on couples that, despite many embryo transfers, have not had any success with pregnancies. We are happy to discuss with you the many advantages and disadvantages of PGS and give you tailored advice as to what the chromosome examination could mean for you and your partner, or respectively, for the child.

What are the costs?

The additional costs for the PGS are substantial. Depending on the number of embryos, one must expect costs of up to ca. 4000 CHF. Feel free to call us on +41 (0)61 261 44 00, email us at or pop by Schifflände 3 in Basel to discuss the costs and create a tailored treatment plan.

Number of embryos with an abnormal number of chromosomes

25 %

Women over 30 Years

35 %

35 Years

60 %

40 Years

85 %

45 Years

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