THAT WAS THEN THIS IS NOW…WHAT A DIFFERENCE A DECADE MAKES IN IVF
When IVF started, cryobiology did not afford the opportunity to freeze embryos. Furthermore, the pregnancy rate per embryo transferred was much lower that it is today. Thus, multiple embryos were transferred so reporting the pregnancy rate by number of live births per retrieval was an accurate reflection of the chance of having a child from one IVF cycle. The risks of this approach were that stimulation treatments were designed to produce many follicles to get many oocytes. Also because the per embryo delivery rate was low, many embryos were transferred at one time resulting in risks of having triplets, quads, quints etc.
Improvements in culture media, medications, and cryobiology have dramatically changed the landscape. Now the goal is to do single embryo transfer and freeze extra embryos to be used in a frozen embryo transfer cycle. This has resulted in the development of “milder” stimulation regimens to reduce the risk of OHSS. The milder stimulation regimens, however, result in fewer oocytes being retrieved in any given cycle. Nonetheless, many couples will have enough embryos to have both a fresh and a frozen embryo transfer from a single retrieval.
DEFINING PRODUCTIVITY TO MAXIMIZE IVF SUCCESS
So the question is: Is there a better way to express the outcome of an IVF cycle? Drs. Stanger and Yovich suggest using what they have termed the productivity rate. The productivity rate is the number of live births per retrieval regardless of whether it was from a fresh or frozen embryo transfer. Consider if a person had a retrieval and generated four embryos and had two transferred fresh and two frozen. If she conceived from the fresh transfer cycle, that would be counted as a pregnancy. If she did not conceive from a fresh transfer, under the present system, it would be counted as a failed IVF cycle. But what if she then had a frozen embryo transfer (FET) and did conceive? That would never show as a successful IVF cycle. Furthermore, when it comes to the patient experience, much of the cost, risk, hassle and intervention occur during the fresh cycle. Transferring frozen requires no stimulation, less monitoring, and no retrieval – only a transfer. Thus the risk of ovarian hyperstimulation and the risk of the retrieval are eliminated. So for very little, if any risk, the person has another chance of conceiving. Strangfer and Yovich suggest expressing the pregnancy rate as the productivity rate combining both the results from fresh embryos transfers with the results of all frozen embryos cycles resulting from that same retrieval. The added frozen embryo transfer does add cost but far less than a fresh cycle.
The current trend is to only transfer one embryo at a time in people who have a high chance for conceiving such as young women or when using donor oocytes. Many of these people will have multiple frozen embryos and with current freezing techniques, the pregnancy chance when using frozen embryos is approximately the same as when using fresh embryos. Especially for couples utilizing donor oocytes or young patients where the female has PCOS, a productivity rate would give a better prediction about actual cost of IVF (financial, psychological and risk) than a fresh transfer pregnancy rate.
GOING THE EXTRA MILE FOR IVF SUCCESS
Couples can now choose to do preimplantation genetic screening (PGS) providing information about the number of chromosomes an embryo has. One of the major reasons for a failed transfer cycle is that the embryo has the wrong number of chromosomes. Using PSG improves the pregnancy rate for single embryo transfers. Combining these technologies, a person can maximize the chance of conceiving using single embryo transfers and thus reduce the overall number of transfers required to achieve a pregnancy.
The use of new technologies and a system utilizing the Productivity Rate, allow patients a better understanding of their chance of success if they are considering using IVF to achieve a pregnancy.