Embryo Freezing

Half the cases of in vitro fertilization result in more embryos than necessary for the transfer since there is a limit to the number of embryo transfers in order to avoid multiple pregnancies. The embryos which are not transferred may be frozen and later thawed when the couple tries for a second child, whenever the first attempt is successful, or when they schedule another transfer for the following month if the first does not achieve the desired pregnancy.

cong1Freezing represents a series of advantages for the couple:

  • when there are embryos in good freezing condition left, this means that the woman responded well to medication for ovarian stimulation, fertilization was adequate and good quality embryos evolved well;
  • the same cycle of ovarian stimulation may result in more than one embryo transfer;
  • if the couple becomes pregnant and does not wish to have any more children, these embryos may, in the near future, be used as stem cells for the treatment of diseases.

However, the freezing of embryos is still a delicate matter which involves a whole series of issues. Some of them are discussed here and if you wish to find out more, write to atendimento@vidafertil.com.br, with “freezing of embryos” as the subject.

Why is it necessary to stimulate the ovaries if a baby comes from just one egg and one sperm?

In a woman’s natural cycle she releases only one egg per month to be fertilized and become an embryo. However, many studies show that the techniques used in ART are not very efficient in the natural cycle. For in vitro fertilization it is necessary for a woman to be submitted to ovarian stimulation through the use of medication in order to produce more than one egg potentially fertilizable. It is important to consider that not all eggs get fertilized and not all fertilized eggs become good quality embryos.

What if I don’t wish my embryos to be frozen?

The Federal Council of Medicine has determined that no more than four embryos can be transferred in each attempt (depending on maternal age). Therefore, a maximum of four eggs may be inseminated whenever the couple does not wish to freeze any embryos since the disposing of human embryos is anti-ethical and illegal.

cong2How will my embryos be kept frozen?

The embryos selected for freezing are placed in a culture medium which avoids extreme cold damage to the cells (they are kept at a temperature of – 196°C) and are stored the following way:
  • The embryos are placed in small tubes (similar to little straws), sealed at both ends, and tagged with the couple’s data. There may be more than one tube per case.
  • The tubes are then placed on a rack and identified once again. Each rack holds between one and three embryos belonging to only one couple.
  • The rack is placed inside a numbered container.
  • The container is placed inside a nitrogen tank also numbered.

What can be done regarding the leftover embryos after deciding we have had enough children?

The couple has two options in this case: saving the embryos for future use as stem cells or anonymously donating the embryos to another couple where both the husband and the wife do not produce good quality gametes to start a child.