There is no standardized reporting method for egg (oocyte) banks that sell vitrified (a method of quick freezing) donor oocytes to patients. This is a proposed option. When percentages are used the denominator should be the number of oocytes thawed. For example the blastocyst rate should be the total number of blastocysts divided by the number of oocytes thawed, not the number of fertilized (2PN) oocytes. The day 5 blastocysts equivalents per oocyte metric is calculated by adding up all of the potential from any embryos transferred or frozen using the table below “Day 5 blastocyst equivalents assigned”. This metric allows for accounting of day 3 embryos transferred and morula stage embryos (50 to 100 cell embryos) transferred on day 5 of growth. Blastocyst stage embryos typically have 200 to 300 cells.
The expected live birth rate (LBR) for 6 oocytes is the theoretical live birth rate if 6 oocytes are cultured to the blastocyst stage and transferred in single embryo transfers until a live birth occurs or there are no embryos remaining. It is calculated as follows:
LBRD5 stands for Live Birth Rate for a Day 5 embryo which for day 5 embryos from donor oocytes is about 45%, or 0.45. This is used standard for all of the oocyte banks. X is the number of day 5 blastocyst equivalents per oocyte for a given cohort (group) of oocytes. A cohort of oocytes is a group of oocytes thawed concurrently in 1 cycle. Typically cohort sizes of 5 to 8 oocytes are used but some cohorts may be as small as 1 oocyte or as large as 12 or more oocytes. The end result is a number between 0 and 0.97 which can be expressed as a percentage from 0% to 97%. The maximum performance by this metric of 97% is the calculated rate of live birth when every oocyte becomes a day 5 blastocyst. This number is calculated using Excel or by hand for each cohort and then the values are averaged among all the oocyte cohorts in a group. For example, in the “All” group in the table below the expected LBR for 6 oocytes of 53% is an average of 164 percentages. This has the benefit of giving a fair representation of the consistency of a program such that each cohort of thawed oocytes is weighted equally regardless of the number of embryos in that cohort.
Here is actual summary data from oocytes thawed at our clinic using these standard reporting methods:
Cryos International is no longer offering oocyte donation services in the United States. This research has been approved by the Christ Hospital IRB (protocol #25-030).
The data in the tables above can be obtained completely from information on the oocyte thaw and embryo creation cycle. No pregnancy outcome data is used. Therefore, its use should be paired with clinical outcome data. The most useful outcome data can be obtained from thawed cohorts of 5 to 8 oocytes. Typically cohorts of this size are used with the intent of obtaining a single pregnancy. Larger sized oocyte cohorts are often used to create embryos for use when genetic testing of the embryos is part of the treatment plan which complicates the analysis.
We find it best to look at cohorts of 5 to 8 oocytes that are thawed for embryo creation where the embryos are either transferred until an ongoing pregnancy occurs or the embryos are transferred until there are none remaining. A typical timeframe for one of these outcomes to occur is 1 year.
Of cohorts of 5 to 8 oocytes thawed for embryo creation with the embryos transferred until an ongoing pregnancy or embryo exhaustion (no embryos remaining) occurs, what percentage result in a live birth? We believe for most donor oocyte cohorts this will occur between 45% and 75% of the time. This appears to be the most important metric of success of vitrified donor oocyte thaw cycles.