Steps of sex selection

PGD (preimplantation genetic diagnosis) for sex selection examines an embryo/embryos for male and female chromosomes. To be able to examine an embryo before transferring it into the uterus in vitro fertilization (IVF) is required. The whole process IVF+PGD for sex selection takes 2,5 weeks and consists of several steps (Fig.2):

• Stimulation of ovaries
• Egg collection
• Egg fertilization outside the body
• Embryo culture in incubator
• PGD for sex selection by FISH method
• Transfer into the uterus of embryo of desired sex
• Treatment after the transfer

Fig. 1. PGD for Sex Selection

Stimulation of ovaries

IVF+PGD procedure starts with stimulation of ovulation. Unlike the natural cycle, hormone stimulation allows for several oocytes to mature. The matured oocytes are retrieved from the ovary to be fertilized. Having several oocytes is vital since not every oocyte may be fertilized as well as not all the embryos have equal chances for pregnancy. It is important to have statistically sufficient number of embryos to find high quality embryos of desired sex.

Hormone therapy is selected individually to ensure that a sufficient quantity of the oocytes matures. It consists of main 2 medications. The first one is FSH hormone (commercial names Puregon, Gonal F), that is identical to the human FSH hormone. Its role is to stimulate development of several eggs in the ovaries. The second medication has many commercial names. It is aimed at prevention of premature ovulation, which is to avoid in IVF treatment.

The reaction of the ovaries to the treatment is monitored by ultrasound. Usually 2-3 ultrasound examinations are required to determine the optimal day for egg collection.

You can read more about stimulation protocols at http://www.avapeter.com/en/infertility/ivf/stimulation/.

The doctor will select the treatment protocol on an individual basis.

Egg collection

When the follicles have reached their mature size (as determined by ultrasound) egg collection is done. About 36 hours before egg retrieval HCG injection is made to finish egg maturation.

The procedure of egg collection is called follicular puncture. It is done under full anesthesia and takes usually 5-10 minutes. Follicular puncture is performed through vagina under ultrasound control. A thin needle penetrates vaginal wall and enters the cavity of a ripe follicle. The follicular liquid containing an egg flows through the needle into a sterile tube (Fig.2).

After the follicular puncture minor pains and small vaginal bleeding can be observed. The procedure does not require hospitalization and is performed on outpatient basis. After a patient is awake the operation results are discussed, and the couple is free to go home until the transfer of embryo to the uterus.

1. Uterus
2. Needle for oocyte retrieval
3. Ovary
4. Ultrasound sensor
5. Vagina
6. Follicle
7. Needle point
8. The oocyte retrieved
9. Test-tube

Fig. 3. Egg collection

Fertilization

The follicular liquid containing an egg flows through the needle in a sterile tube (Fig.2).

On the same day a partner delivers sperm for fertilization. Frozen sperm can also be used.

Thus fertilization outside the body becomes possible.

If sperm is fresh and of good quality, the conventional IVF procedure is made. If the sperm was frozen some time ago and/or motility of sperm is not optimal ICSI method is used (see Fig. 3). Under ICSI we unersand microinjection of a sperm in an egg.

Fig.4 ICSI

The morning after the oocytes have been collected our specialists in the IVF laboratory check to see if fertilization has occurred. There are two pronuclei in a fertilized ovum, one is from the sperm and one is from the oocyte. The pronucleus of the sperm determines the gender of the embryo. Within a few hours, the pronuclei join together and form the nucleus of the cell. The nucleus contains the chromosomes, including chromosomes X and Y that determine the gender.

The fertilized oocytes continue to be cultivated untill day 3 after egg retrieval in an incubator where the temperature and amount of carbon dioxide are carefully regulated. On day 3 after follicular punctuer PGD fir sex selection starts.

PGD for sex selection

At day 3 after egg collection one cell is taken out of each embryo to be analized for chromosomes X and Y. This process is called blastomere biopsy. To undergo blastomere biopsy each embryo must have 6-8 cells (blastomeres) which is normal for this day of development.

After the blastomere biopsy all the embryos continue their development in the incubator where the temperature and amount of carbon dioxide are carefully regulated. The biopsied blastomere represents the embryo, it was taken from. Between days 3 and 5 after egg retrieval, as embryos continue their development in the incubator, the blastomeres are fixed on the glass and studied for male and female chromosomes by FISH method. If a blastomere has Y chromosome, the embryo it was taken from is of male sex, otherwise - of female sex.

Fig.5 PGD principle

PGD method studies not only sex chromosomes. It can reveal seriouse disease such as Down syndrom. If you plan PGD for family balancing (sex selection), use opportunity to check your future baby for Down syndrom and other chromosome diseases.

Embryo transfer

Fig. 6. Embryo transfer

Embryo transfer is a simple and painless procedure that takes place on day 5 after the oocyte retrieval. By day 5 the result of PGD for sex selection is ready. The embryo is transferred using a very thin soft plastic catheter which is introduced into the uterus via the vagina and cervical canal. In our practice we transfer only one or two embryos, to avoid multiple pregnancies.

The remaining high-quality embryos may be frozen at a very low temperature for the next possible attempts or pregnancies (embryo cryopreservation).

After the embryo is transferred into the uterus, progesterone and estrogens are used to support the implantation. The first pregnancy test is made two weeks after the transfer.

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