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Should Fertility Clinics Utilize Both Early Cleavage Embryo Transfers and Blastocyst Transfers?

D. Vaughn, L. Murphy, E. Seidler, A. Penzias, D. Sakkas, W. Neuhausser

August 12, 2019
Bridget Houlihan

There have been many medical advances over the years when it comes to embryo culture transfer, and today most fertility clinics choose to employ the blastocyst transfer. But a study done by the Boston IVF set out to look at the implantation rates of early cleavage embryo transfers versus blastocysts transfers. The researchers were concerned that there might be embryos lost in vitro that do not develop between days two and three until day five-- while in vivo they might have the opportunity to implant. This is particularly important for women who do not have many embryos available.

This article will discuss:

  • The difference between early cleavage embryo transfer and blastocyst transfer
  • What the results of the study discover about the viability of implanting embryos in different stages
fertilized cells viewed under a microscope
This study examined the outcomes of embryonic transfers at the cleavage stage and the blastocyst stage. Image courtesy of Atlas of Human Embryology.

What is the Difference Between Early Cleavage Embryo Transfer and Blastocyst Transfer?

Embryo transfer refers to the fertility treatment process that transfers the embryo into the uterus of a woman, with the hope of it implanting and developing into a pregnancy. An early embryo transfer refers to placing an embryo that has been cultured for 2-3 days after fertilization into the uterus. If the patient happened to have any embryos in this stage that were not used in implantation, they can be frozen and stored for future use in case the process is not successful.

If there are multiple embryos that develop after fertilization, fertility specialists will see if extra days (typically around day five after fertilization) will allow them to develop into blastocysts. Infertility studies have shown that blastocyst transfer can have a higher success rate for implantation-- compared to the early cleavage embryo transfer. This has caused many clinics to focus solely on blastocyst transfer, and lead the researchers behind this study to wonder if this might not be the only option for patients striving for implantation.

Study Objective and Method

This study sought to examine the different outcomes of patients who had less than five 2PN embryos, and who either utilized early cleavage transfer or blastocyst transfer. It also looked at patients who had poor cleavage stage embryos which were transferred at this stage, to those patients who had poor cleavage stage embryos but waited until the blastocyst stage to complete the transfer.

The patients in this study all had oocytes removed from 2013 through 2016, and whose transfers were fresh as opposed to frozen. Cases were included in the cleavage transfer group if the patient had one or more embryos transferred at the cleavage stage on day two or three, as well as those patients who had embryos on day one. Patients were included in the blastocyst transfer group if they had one or more embryos transferred on day four through six.

diagram of a blastocyst
Measuring the birth rate of both embryonic transfers may assist in deciding which offers the most benefit to individuals. Image courtesy of the Cleveland Clinic.

Results and Conclusions

Patients younger than 38 years old

There 1,183 patients whose data was reviewed for this study, and their results were broken down into two categories-- those who were less than 38 years old at transfer, and those that were older than 38 years old at transfer. For those patients who were younger than age 38, there were 668 embryos transferred at the cleavage stage. This resulted in a 21.4% implantation rate and 122 live births. Out of the 409 women who underwent transfers in this group, there was an 18% rate of a live birth via the transfer at the cleavage stage.

For women who were 38 or younger, there were 202 embryos transferred at the blastocyst stage on day five or six. These transfers resulted in a 40.6% implantation rate and amounted to 76 live births. There were 153 transfers done at the blastocyst stage, which amounts to a 38% rate of a live birth.

Patients older than 38 years old

Of the 538 women who were 38 years and older who had 1312 embryos transferred via a cleavage transfer, there was a 7.5% rate of implantation and 61 live births. Out of this subset, this accounts for just 5% of women who gave birth in this group. The 83 women who were 38 years and older and had 155 embryos transferred via a blastocyst transfer had an implantation rate of 19% and 22 live births.

These results show that there is a higher rate of attrition among poor quality in vitro between day three and day five than there is in vivo. The researchers also noted that the birth rate among the transfers at the cleavage stage was poor, however the total live birth rate among blastocyst embryos of 28.6% was encouraging.

The data shows that there are differences between the success rates of the two embryonic transfer techniques, and while these can be dependent upon many factors-- including age-- the researchers suggest more in depth trials to investigate further.


Non-inferiority of Cleavage-Stage Versus Blastocyst-Stage Embryo Transfer in Poor Prognosis IVF Patients (PRECiSE Trial): Study Protocol for a Randomized Controlled Trial

Reproductive Health -  17, Article number: 16 (2020)


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