Embryo Transfer

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A blastocyst is an embryo that has developed for five to six days after fertilization. With blastocyst transfer, embryos are cultured in the laboratory incubator to the blastocyst stage before they are transferred to the womb.

A. Blastocyst culture is indicated for :

Patients who had repeatedly failed to achieve a pregnancy following the transfer of good quality cleaved embryos (If the growth of the embryos arrests and they do not develop to blastocysts, this may indicate a potential egg problem)


B. Procedure :

After the process of in vitro fertilizations (IVF), embryo s formed. Each egg is evaluated for evidence of fertilization. It takes about 18 hours for the egg to be fertilized. The first sign of fertilization is the presence of two small dots inside the egg called pronuclei- one from the sperm and one from the egg. The fertilized egg is called a zygote. The eggs that have fertilized are allowed to develop for two or more additional days. About 12 hours later, the fertilized eggs start to divide into two cells, and subsequently into four and so on. By day 3 the embryos have cleaved (divided) into 6-10 cells and ready for replacement into the woman’s uterus.The transfer of several embryos increases the probability of success. A multiple embryo transfer also increases the risk of a multiple pregnancy. Embryos are transferred on either day three or day five of development.

B. Procedure :

After the process of in vitro fertilizations (IVF), embryo s formed. Each egg is evaluated for evidence of fertilization. It takes about 18 hours for the egg to be fertilized. The first sign of fertilization is the presence of two small dots inside the egg called pronuclei- one from the sperm and one from the egg. The fertilized egg is called a zygote. The eggs that have fertilized are allowed to develop for two or more additional days. About 12 hours later, the fertilized eggs start to divide into two cells, and subsequently into four and so on. By day 3 the embryos have cleaved (divided) into 6-10 cells and ready for replacement into the woman’s uterus.The transfer of several embryos increases the probability of success. A multiple embryo transfer also increases the risk of a multiple pregnancy. Embryos are transferred on either day three or day five of development.


With 2 – 3 good embryos on day 3 we at ACME fertility clinic & IVF center advise a day 3 transfer as
  • 1. The pregnancy rate between day 3 and day 5 transfer remains the same.
  • 2. 40% of patients will not grow blastocysts
  • 10% of the embryos that fail to develop to blastocysts in vitro may have done so if replaced inside the womb on day 3.

C. Blastocyst Transfer :

After 5-6 days the embryo advances in development and becomes a blastocyst. Blastocyst transfer is claimed to be more physiological than cleaved-embryo transfer as it mimics nature more closely.The improved implantation rates following blastocyst transfer is due to selection of the best embryos as it gives a better idea of the competence of an embryo.There should be at least 4 good embryos on day 3 to benefit from this procedure.Patients who wish to achieve a pregnancy without the risk of high order multiple pregnancy, Transfer of one or two blastocysts avoids multiple pregnancies

D: Pros and cons of blastocyst transfer :

Blastocyst transfer can be highly successful for some groups of women, but it isn’t right for everyone and does have some drawbacks:

  • 1. Blastocyst transfer can result in a higher likelihood of becoming pregnant when compared with 2–3 day embryo transfer in certain groups of women.
  • 2. But if you opt for blastocyst transfer, you may not get any embryos that develop to the blastocyst stage.
  • 3. There may also be fewer embryos to freeze.
  • 4. Even if you have only one blastocyst replaced there is still a small risk of twin pregnancy. This is because at the very early stages of development blastocysts can split to give monozygotic (identical) twins.
  • 5. Blastocyst transfer may not be suitable for all women.

E: Blastocyst transfer & risk of multiple birth :

Blastocyst transfer appears to increase the chance of a live birth, particularly for mothers under the age of 35. Unfortunately, when two blastocysts are transferred, it also greatly increases the risk of multiple births – some studies suggest it increases the risk even more than transferring 2–3 day embryos. It is thought that this is because only better quality embryos will survive for 5–6 days before transfer, so they are even more likely to implant themselves in the womb. A study in 2005 found that after double blastocyst transfer the twin pregnancy rate was 62%, compared with only 3.2% after a single blastocyst transfer.

F: Other Types of Gamete Transfers :

a :GIFT -Gamete Intra Fallopian Transfer :

It is a laparoscopic procedure where the oocytes are aspirated, identified and mixed with prepared sperm and then deposited into the Fallopian tube. The Fallopian tubes and sperm must appear normal on investigations, prior to the procedure. It is no longer popular as it involves a laparoscopy. Also, if the patient does not conceive, we do not know whether it was because fertilisation did not take place. It still has a place in the treatment of infertility in those patients who for religious reasons are forbidden to allow fertilisation to take place outside the body.

b :ZIFT- Zygote Intra Fallopian Transfer ::

This procedure was developed to overcome the drawbacks of the GIFT procedure. In Zygote Intra Fallopian Transfer the eggs are aspirated by transvaginal ultrasound and the fertilised eggs (zygotes) are transferred into a normal fallopian tube by laparoscopy. It was recommended for male infertility as fertilisation of the eggs could be confirmed. It was popular earlier as culture conditions were not optimal for embryo culture- it was believed that early transfer of the zygotes into its natural environment would be more beneficial. Today embryos are transferred into the fallopian tube only if the cervical transfer is expected to be difficult.