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There are many embryo grading systems that embryologists use to evaluate embryos for transfer. The ASRM (American Society of Reproductive Medicine) has attempted to establish a standard grading system, so when a patient or previous clinic is talking about "the quality of the embryos", it can be interpreted and understood by the clinic she is now at, which is important in trying to understand why her cycle of IVF was unsuccessful and what "changes" can be made to result in a successful outcome. Even with standardized grading systems, which is still not universally used, evaluation and scoring of any stage of embryo development, from fertilization to a hatching blastocyst is critical to the experience and expertise of the embryologist.
After oocyte (egg recovery), the eggs are placed in the incubator for a number of hours before they are checked for maturity. At that time, the embryologist will remove the cells surrounding each egg (cumulus cells) and check the egg for maturity. Each mature egg will undergo ICSI, and be placed back in the incubator. The following day the embryo will be checked for fertilization but is not graded. The embryos will not be checked again until day 3, 4, or 5 (blastocyst) depending on when the transfer was planned. At that point in time, the embryologist will check each embryo and "grade" it, picking the best for transfer, and he will determine if the remaining ones are suitable for cryopreservation.
Grading of a day 3 embryo is based on the number of cells that make up the embryo, the amount of fragmentation, and the symmetry of each of the embryo's cells (blastomeres).
In summary, a "perfect" day 3 embryo should be 8AG - eight cells, no fragmentation and all the cells are equal and symmetrical. Human embryos are so variable, and although scoring is very important in helping to decide which embryos to recommend for embryo transfer and which to freeze, embryo quality as evaluated under the microscope, even by very experienced embryologists, ultimately is only a reasonable "estimate" of predicting the chances for a successful pregnancy. Any good embryologist will tell you that "even though an embryo(s) looks good, it doesn't mean that it is good" and visa versa.
Scoring of blastocysts are similar but have a completely different set of scoring criteria. Blastocyst quality is determined by evaluating the outer ring of cells, known as the trophectoderm or trophoblastic cells, that will eventually form the placenta; the inner cell mass or ICM, which is made up of the stem cells, that the baby will develop from; and finally, the degree of expansion of the blastocyst cavity and whether or not it has started to "hatch" or break out of its zona pellucida or "shell". Again, scoring of a blastocyst depends on the experience and expertise of the embryologist. Like day 3 embryos, scoring of even blastocysts is an imperfect science, and some very nice looking blastocysts do not produce a pregnancy; whereas, less than optimum ones do. However, the basic rule of thumb is "that the best of the best embryos" make it to the blastocyst stage, and a very nice blastocyst has a greater chance statistically of producing an ongoing pregnancy than a lesser quality one.
Since there are many other contributing factors involved that we cannot see or identify, embryo scores are, at best, generalizations about "quality" and are often inaccurate. Many times, Arizona Center for Fertility Studies has seen cycles fail after transferring 2-3 "perfect" looking embryos; and many times see successful ongoing pregnancies after transferring only one "decreased quality" embryo. The actual "potential" of the embryo to implant and continue normal development is impossible to accurately measure and predict with current technology. Although some clinics will cancel the embryo transfer if there is only one embryo or several embryos of "poor quality"; for the above reason and based on extensive experience, Arizona Center for Fertility Studies will always recommend transferring one embryo, even if it did not get the "best" scoring. "Bad embryos" do not cause "bad babies", they cause no babies. Therefore, as long as there is even the slightest chance of success, Arizona Center for Fertility Studies recommends the transfer of "less than optimum" embryos.
One additional thing that is very important is the embryo transfer. A traumatic and/or bloody difficult transfer can result in decreased pregnancy rates probably by disrupting the endometrial lining, introducing blood into the uterine cavity, triggering an inflammatory reaction, or by just having the embryos exposed to the outside environment, as opposed to the incubator environment, for too long. At Arizona Center for Fertility Studies, several months before an embryo transfer, a mock transfer is done to measure the depth of the uterine cavity, the degree of angulation and direction of the cervical canal and the ease or difficulty of eventual embryo transfer. At the time of the actual embryo transfer there should be no surprises. At Arizona Center for Fertility Studies, embryo transfers take less than 30 seconds from the time the embryos are removed from the culture environment of the incubator to being loaded in the transfer catheter.
Ultimately, the true test of embryo quality is whether it results in a successful pregnancy and live birth. IVF is not an exact science, and when nothing has been overlooked, the woman has a reasonable FSH level and she is at a clinic with proven high success rates, than a successful ongoing pregnancy, is for the most part, with a few exceptions of very poor sperm quality even with ICSI, determined by the overall genetic quality of the egg. A thousand things can effect that, most of which we can not determine and/or correct. With controlled ovarian stimulation, Arizona Center for Fertility Studies tries to get as many eggs as genetically predetermined in each individual woman. The more eggs you get (balancing avoiding OHSS) the more possible embryos a woman has, the greater the percentage that the embryologist can find "good quality" embryos to transfer and enough to freeze. However, there are plenty of women that are "low responders"; they do not make a lot of eggs/embryos, but the ones they make are "excellent" and result in a successful pregnancy. But successful IVF may take more than one attempt. Each stimulation cycle is an independent cycle and is usually different than the previous one. If the first IVF cycle is not successful, Arizona Center for Fertility Studies has learned a tremendous amount of information about the woman and can change things with the next attempt. Thousands of previous cycles have "told" us what to do on that initial attempt, but every woman is unique and you can only conclude "generalizations" about what is the best protocol for any particular woman or age group.
"We've been meaning to write/send pictures for awhile, but have been quite busy since the birth of our twins. We sincerely want to thank you for all the love and support you gave us throughout this whole process. Dr. Nemiro- when we first met you it was under one of the most difficult times of our life as I was having an ectopic pregnancy which ultimately required removal of my left tube after having already suffered one miscarriage. All this had occurred after 2 prior failed IVF attempts with another doctor. Even though you had never met us, you agreed to perform an emergency surgery at 8 pm without any hesitation. We were terrified and heartbroken during our 1st visit with you due to our unfortunate circumstances but you put our minds at ease and assured us you would do all you could to help. Unfortunately, my tube was to damaged to save and then you had the unfortunate task of having to tell me that my remaining tube was unlikely to ever result in a viable pregnancy. Following the surgery, we were totally devastated and without hope. I felt I didn't want to go on if I couldn't bear children, but you convinced us to give IVF another try with a more aggressive drug protocol than had been previously utilized. We'll never forget the night you transferred our embryos. You told us they all "looked" good but that 2 looked particularly good. We knew from that moment that we were finally going to achieve our dream of having children. The rest is history, we now have two beautiful, healthy babies and we just wanted to express our sincere gratitude to you and your staff. Everyone in your office was always so supportive and compassionate. Even after achieving pregnancy I had weekly, sometimes daily "scares" due to bleeding, during my first trimester. Everyone always took the time to reassure me and give me as many ultrasounds as I felt I needed to put my mind at ease and every time I thought my pregnancy had ended, I was assured my babies were still very much alive and thriving. Thanks again for everything and for helping us along on our journey. Love."
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