Selective single blastocyst transfer reduces the multiple pregnancy rate and increases pregnancy rates: a pre- and post intervention study
The above study and the discussions that accompanied its publication, highlight the following messages:
1. Multiple pregnancy is the single biggest risk to the health of babies conceived by IVF; this is due to the high likelihood that the babies will be born prematurely, or be lost earlier in the pregnancy. Twins are 20 times more likely after IVF than being conceived naturally.
Twins have:
5x chance of cerebral palsy
4x chance of dying shortly after birth
3x chance of stillbirth
2x risk of disability
Thus twin pregnancy should not be seen as the ideal outcome of IVF treatment and should be avoided where possible.
2 - Replacing one embryo at a time will solve the problem, but is not appropriate for all patients, as some will require more than one embryo just to become pregnant at all.
3 - Restricting the number of embryos transferred in an IVF cycle to one as a blanket policy would disadvantage many patients, and we do not advocate this as a policy for UK.
4 - However continuing with the status quo, where two embryos are replaced in most cycles will perpetuate the high and increasing multiple birth rate, and will continue to damage some babies and their mothers. We believe this is professionally unacceptable and irresponsible.
5 - It is clear from the literature and from our experience that a single blastocyst transferred on day 5 gives a substantially higher chance of pregnancy than an embryo replaced on day 3 of development.
6 - We have proposed that patients who have the highest chance of getting pregnant after embryo transfer, and are thus most likely to conceive twins if two embryos are replaced, are offered single blastocyst transfer which has a very high success rate (over 50%) and a very low rate of twins (those in whom the blastocyst splits to form identical twins). Not surprisingly this proposal has been met with some scepticism from some colleagues as they feared that this strategy would be unacceptable to patients, and would lead to a drop in the overall success of a given clinic and could affect their place in the so called "league tables".
7 - What our study demonstrated was that by adopting a comprehensive educational package, the majority of eligible patients were willing to accept single blastocyst transfer and did not suffer as a result of this decision.
8 - By targeting this very high risk group (best prognosis patients), which constituted only 20% of our patients, we have been able to halve our multiple pregnancy rates, and, contrary to the sceptics opinion, not only did we maintain our success rates in the overall programme but we managed to increase
them over the course of the study.
9 - We are encouraged by our experience and we would urge other clinics to look at it and see if they can reproduce our results.
10- We accept that for the same group of patients who received a single blastocyst transfer, the transfer of two blastocysts could have resulted in a slightly higher pregnancy rate, but at the expense of significantly higher multiple pregnancy rates (62% in one USA report) with all the risks to the pregnancy, the mother and the babies that that twin pregnancy could entail. The careful reader of our paper will recognise that our policy also resulted in an increase in the number of cycles where embryos were suitable for freezing which is an additional chance of a pregnancy from a single stimulation cycle. We will report on the cumulative increase at a later stage.
Further information
For more information, read the full article on Blackwell Synergy's website.