Familiar scenario: High on hopes and hormones, emotionally and physically prepared for frozen embryo transfer and just about to leave home for this aniticpated procedure, the patient receives the dreaded call from an IVF center staff-person: “Your embryos didn’t make it. There will be no transfer. Stop your meds. Call with a period. Sorry.”
And you were told that your embryos were “good enough to freeze”. Maybe good enough to freeze but not to thaw? What went wrong? A doctor-patient conference should be the immediate next step and the savvy patient will be able to learn enough from this meeting to help her decide how to proceed with future treatment.
Once an egg has been fertilized (either by conventional insemination or via ICSI,the injection procedure) it must divide and develop for five days before it becomes a blastocyst – the stage at which it may initiate implantation. The preembryo or 2PN stage is observed on “Day 1″. Days 2 and 3 denote the cell stages. The cells continue to divide but compact into an amorphous morula on Day 4 and, by Day 5 or 6, a healthy blastocyst will demonstrate sufficient stem cells to make a human being. An embryo can be successfully frozen on any of these days but the ultimate potential of this tissue depends upon its genetic normalcy, the day upon which it was frozen, and the freezing method that was employed.
An average of 50-60% of all growing embryos normally arrests between days 3 and 4 because of genetic incompatibilities of the eggs and sperm that formed them. (This percentage increases as a woman ages.) Cryopreserving cell-stage embryos (before this selection has occurred) may therefore be creating false hope in the freezer as particular embryos frozen on day 2 or 3 may have been destined to arrest in the first place.
The day on which an embryo is frozen will also affect its ability to survive once thawed. Embryos freeze and thaw well at the 2PN and blastocyst stages with survival upwards of 90%. Cell-stage embryos, however, fare far worse as only about 25% of these survive with all their cells intact. A higher percentage of thawed cell-stage embryos may initially survive but with a loss of 50% of their cells, and a patient may be a recipient of these “technically viable” embryos which have no chance of proceeding to pregnancy.
The aforementioned percentages represent the traditional “slow-freeze” method of embryo cryopreservation. This reliable technique is being replaced in most IVF centers with the newer vitrification method. To date, thaw and pregnancy rate numbers are better with vitrification but there is not yet enough data demonstrating, definitively, its superiority over the slow-freeze method.
Armed with the above the disappointed patient should meet with her doctor to review sequential photos of her embryos and to discuss the particulars of her case. How many embryos were frozen, at what stage, and by what technique? Were these supernumary embryos a step down in quality from the ones that had been formerly transferred on a fresh cycle? Does the abysmal outcome portend similar failures in subsequent attempts?
Oftentimes patients are told that they may discuss their concerns with their doctor in 3 – 4 weeks. This lengthy wait serves only to prolong anxiety and compromise trust in the physician. If the doctor cannot meet with the patient within a day or two of the cancelled transfer a phone call or even a letter from him/her (personal, private, Fed Ex if necessary!) will suffice. It is the patient’s right to request a dialogue. Communication is key.