Deciding how many embryos to transfer is not an easy decision and raises many questions. Some patients are not comfortable with the concept of embryo freezing and thus elect to transfer all viable embryos. Obviously, the RE needs to be aware of this plan and such patients may need to restrict how many eggs are fertilized in order to avoid becoming the next Jon and Kate plus Eight.... Usually, 50-75% of the eggs will fertilize and half of these will develop into embryos that are good enough to transfer or to freeze BUT this is not always the case....I have seen 6 good embryos from 6 eggs and 2 good embryos from 23 eggs...go figure.
So how can we make educated decisions about the number to transfer? Well that is the Question of the Day!
50. How do I decide how many embryos to transfer?
Determining the number of embryos to transfer in an IVF cycle is a crucial decision that requires careful discussion between the patient/couple and the physician. The goal of every treatment cycle should be the delivery of a full-term, healthy, singleton baby. Although transferring more than one embryo will increase the pregnancy rate, at some point transferring additional embryos merely serves to increase the multiple pregnancy rate without altering the overall pregnancy rate. Several European countries have eliminated all discussion of how many embryos to transfer by mandating that all patients undergo only single-embryo transfers. Whereas elective (or mandatory) single-embryo transfer has been promoted heavily throughout Europe, it has not yet received widespread acceptance in the United States although this attitude may be changing slowly.
One of the major disadvantages of single-embryo transfer is that it leads to a decreased IVF pregnancy rate from the fresh cycle. Proponents of single-embryo transfer claim that the potential reduction in the overall pregnancy rate is well worth the marked reduction in the twin pregnancy rate. Twin pregnancies can be problematic because they are associated with higher rates of preterm labor and preterm delivery. Some couples, however, may desire twins or at least regard them as a neutral outcome. This view is especially prevalent among patients who are paying for the treatment themselves (rather than it being covered by insurance) and regard twins as a “two for the price of one” outcome. As noted in Question 49, the greatest risk to the health of children following IVF is the complications related to prematurity associated with multiple births. Despite the risks associated with multiple pregnancy, couples still tell us every day that they would “love to have twins.”
In the U.S., there is no question that the trend is to transfer of a single embryo in most patients. We fully embrace this concept. In fact, with the recent advances in embryo cryopreservation, such as vitrification our frozen-thawed embryos seem to be as likely to implant and produce a healthy pregnancy as embryos transferred in a fresh cycle. This, in the patients classified as “Most favorable prognosis” we see no need to transfer more than a single embryo and risk a multiple pregnancy when we can safely perform a frozen-thawed embryo using high-quality vitrified embryos. However, convincing patients has proved more difficult. One of the advantages of Natural Cycle IVF is that there is rarely the option to transfer more than a single embryo since nearly all patients produce only a single mature egg in a typical reproductive cycle. Some patients who had planned to undergo single embryo transfer will change their mind at the last minute and elect to transfer 2 embryos greatly increasing the risk of a twin pregnancy. With Natural Cycle IVF the temptation to transfer two embryos has been eliminated entirely.
The ASRM has published guidelines for making the decision of how many embryos to transfer (see Table 1). Patients who fall into the excellent prognosis category should transfer only one or two embryos, whereas those with an exceedingly poor prognosis—because of the woman’s age or multiple failed IVFs, for example—may undergo embryo transfer of five or more embryos.
The most problematic decisions concern those patients who fall between these two extremes. Couples who are paying out of pocket for IVF will often pressure their RE to be more aggressive in terms of the number of embryos transferred. Of course, the expense involved in caring for premature infants is many times greater than the cost of all of the fertility procedures used to initiate those pregnancies. The financial costs are merely one part of the picture, as caring for patients with preterm labor or premature infants is also associated with a variety of emotional, psychological, and physical costs.
If multiple pregnancies occur, a multifetal selective reduction procedure can be considered. This procedure is performed at approximately 10 weeks of pregnancy and involves injecting a salt solution into one or more of the gestational sacs. The overall pregnancy loss rate following this procedure is usually less than 5%. In patients who wish to avoid a triplet gestation (but who will not consider selective reduction), it is best to limit the number of embryos transferred to one or two.
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