What Does Days Post-Retrieval (DPR) Mean?
Days post-retrieval is a common method used to count the number
of days that pass after a woman’s eggs are retrieved for in-vitro fertilization
(IVF). There are several significant milestones that occur after egg retrieval
that are measured in days-post-retrieval; these include fertilization,
evaluation of fertilized eggs, and transfer of fertilized eggs into the uterus.
FertilitySmarts Explains Days Post-Retrieval (DPR)
During an egg retrieval procedure, multiple egg-containing follicles are removed from a woman’s ovaries and the mature eggs are then fertilized in a lab. The resulting embryos can then be transferred back into the patient’s uterus for implantation and hopefully pregnancy. The retrieved eggs are carefully watched by an embryologist after fertilization to monitor their development. Some significant milestones:
One day post-retrieval – This is the day after the egg retrieval procedure. About 18 hours after the egg is retrieved, it is fertilized by either mixing it with the sperm or by injecting a sperm directly into the egg using a fine needle with intracytoplasmic sperm injection (ICSI).
Two days post-retrieval – Eggs are examined to make sure that fertilization occurred properly. Only eggs that were fertilized properly will continue to be grown in the lab. By 2 days post-retrieval, the fertilized eggs have undergone cell division and are now 2 or 4 cells instead of 1.
Three days post-retrieval – If the embryos show good development, embryologists can select the best quality embryos for implantation on day 3. If the embryologists have any doubt as to the quality of the embryos at this point, however, the embryos are allowed to continue to grow to day 5 and monitored until then.
Four days post-retrieval – By 4 days post-retrieval, many different development stages can be seen. Embryos should be 10 cells or more at this point and should be compacting together into a ball shape called a morula. Only good quality embryos will develop to this point so any specimens that were weak will have been removed from the growth medium.
Five days post-retrieval – Embryo transfer generally occurs on day 5, if it wasn't done on day 3 (assuming transfer is happening during the patient's current menstrual cycle). Many of the embryos that formed ball shapes on the previous day should have developed into blastocysts by day 5. A blastocyst is a sphere of cells around the outside with a small mass of cells on one wall inside, like a balloon with a ball inside. Embryologists can evaluate the blastocysts and assign each one a grade based on the quality of the outer surface (the trophoblast) and the inner clump of cells (the inner cell mass). Only the most developed, best quality embryos will be selected for transfer on this day. Any extra, good quality embryos can be frozen on day 5 or 6, and used in the future.