Embryo Culture

If you and your partner are about to undergo IVF treatment, or if you are considering pursuing the IVF process, than it is important to know as much as you can about the steps involved. IVF is a very delicate process, and it is essential that all steps are performed correctly in order for it to be successful. One of the most important parts of IVF is the embryo culture stage. It is during this stage that an embryo will be formed and nurtured until it is ready to be transferred into your uterus.

What is Embryo Culture?

Embryo culture is the term used to describe the process immediately following egg retrieval (either from stimulation or through a donor bank)

. It is during the culture process that your eggs and your partner's sperm will be combined in order to produce a fertilized egg (known as an zygote). Once a zygote has been formed, the culture process will continue in order to encourage the growth of the zygote into an embryo. Lasting from 2 to 5 days, the embryo culture process is vital to the success of any IVF procedure. Without accurate and controlled embryo culture, IVF transfer may not be successful.

The First Step: Fertilization

Immediately following your IVF retrieval, any aspirated follicular fluid will be transported to your fertility clinic's laboratory. Here, your follicular fluid will be examined under a microscope, in order to identify all eggs that are present. Each egg and its surrounding cells will then be washed in a special medium, in order to remove any toxins and impurities. These eggs will then be transferred, in separate dishes, to a special incubator containing carbon dioxide. The eggs will remain in this incubator until fertilization is ready to take place. This usually happens between two and six hours after egg retrieval, depending upon the maturity of the eggs.

When the eggs are matured, they will each be combined with some of your partner's sperm. His sperm will have been washed and divided up into specific amounts. Typically, no more than 100,000 sperm per milliliter are used during the fertilization procedure. The sperm and egg will be combined in a dish that contains special culture medium. This culture medium, made up of protein, salt, and antibiotics, is designed to help the embryo during the first days of division. The dish is then placed back inside of the incubator.

Monitoring the Embryos

Your developing embryos will be monitored carefully by an embryologist, a person who specializes in embryo development for IVF and other fertility treatments. After 18 hours of development, your embryologist will make the first check on your embryos. By this stage, your embryos will still be single cells. However, they will contain two clear bubbles (known as pronuclei) inside. These pronuclei are evidence that the embryo contains genetic material from both you and your male partner. Embryos without pronuclei are discarded.

Your embryos will then be left to develop for another 24 hours. At this point, embryos will be monitored for cell division. Most embryos have developed into two or four-cell embryos at this point. Some laboratories will allow embryos to continue culturing, while other labs will proceed with embryo transfer at this point. Depending upon your particular health needs, you may or may not choose to have a transfer done at this point.

How Long Should an Embryo Be Cultured?

Embryos can be cultured for a various lengths of time, depending upon the reproductive history of you and your partner. Embryos can be cultured for:

  • Two Days: Embryos that are cultured for two days are generally transferred at the two or four-cell stage. This type of transfer is beneficial for couples who have a low number of embryos available for transfer, or who have embryos that are developing poorly.
  • Three Days: Embryos that are cultured for three days are usually transferred at the six to eight cell stage. Many laboratories prefer to culture embryos until this stage because it allows for increased monitoring. Embryos cultured for three days can be checked by the embryologist for gene activation and cleavage, which improves the likelihood of transferring a viable embryo.
  • Five Days: Embryos that are cultured for five days are transferred at the blastocyst stage. Blastocysts consist of 12 to 16 cells and are well on their way to be ready for implantation into the uterus Many labs opt to transfer at the blastocyst stage, particularly if you have had repeated miscarriages or IVF failures.

Environment and Embryo Culture

The environments in which your embryos are cultured are of the utmost importance when it comes to completing the culture stage successfully. Some essential components in IVF culture environments include:

  • Culture Medium: All developing embryos are cultured is a special medium, designed to help them develop and grow. There are generally two types of culture mediums used by laboratories: one is for initial embryo development (up to 3 days) and the second if for later development (up to blastocyst stage).
  • Temperature: Embryos need to be cultured at a specific temperature to ensure survival. The temperature inside of the embryonic incubators is maintained at 37 degrees Celsius. This is the same temperature that is found inside of your fallopian tubes.

Emotions and Embryo Culture

The embryo culture stage is often one of the most frustrating parts of IVF treatment. It is during this stage that you and your partner will find out how many embryos were successfully fertilized and how many are available for transfer. In order to stay sane during this stage or treatment it is important to take time out for yourself. Try not to focus on the development of your embryos, but instead relax, watch television, or meditate. Information will come soon enough.


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