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 United States, there is no question that the trend is to transfer a single embryo in most patients. We fully embrace this concept. In fact, with the recent advances in embryo cryopreservation, such as vitrification (see Question 72) frozen-thawed embryos seem to be as likely to implant and produce healthy pregnancies as embryos transferred in a fresh cycle. Thus, 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 minds at the last minute and elect to transfer two 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 5). 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.

Table 5 Recommended Limits on the Numbers of Embryos to Transfer

Age
Prognosis < 35 yrs 35–37 yrs 38–40 yrs 41–42 yrs
Cleavage-stage embryosa
Favorableb
All others
1–2
2
2
3
3
4
5
5
Blastocystsa
Favorableb
All others
1
2
2
2
2
3
3
3

a Justification for transferring one additional embryo more than the recommended limit should be clearly documented in the patient’s medical record.
b Favorable = first cycle of IVF, good embryo quality, excess embryos available for cryopreservation, or previous successful IVF cycle.
Source: Adapted from Guidelines on the number of embryos transferred. The Practice Committee of the Society for Assisted Reproductive Technology and the American Society for Reproductive Medicine. Fertil Steril 2009:92:1518-19. Copyright 2009 American Society for Reproductive Medicine.

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.

Kristin comments:

During my first IVF cycle, we transferred two embryos. This was the standard at our clinic based on my age.When the attempt failed, I was ready to increase the number of embryos transferred to three to increase my chances of getting pregnant. I began another fresh IVF cycle and, when we got close to the transfer, I discussed my desire to transfer three embryos with my RE. He suggested we wait to make the decision based on our embryo quality.

On the day of my transfer, the embryologist refused to transfer more than two embryos because he deemed the two best to be of excellent quality. When I became pregnant with twins, I was extremely thankful that my doctors held their ground and did not let me talk them into transferring more embryos. I had a very difficult pregnancy. If my husband and I decide to try IVF again, we will seriously consider transferring one embryo to reduce my risk of carrying multiples again.

Rebecca comments:

I was on the opposite end of the spectrum as Kristin (see preceding comments). I was weeks away from turning 41 during my first IVF attempt. When we learned that we had six blasts available for transfer, we just assumed that we would transfer two and freeze the rest. Our RE counseled us to transfer all. This was extremely concerning to us, but our RE explained that multiples, especially high order multiples, would be EXTREMELY rare at my age, and that he felt the most aggressive approach (that would also save precious time and money) would be to transfer all. This same office scenario played itself out two more times, until our 3rd, and successful, IVF. For us, it took the transfer of a total of 18, five-day blasts to finally bring our boy/girl twins into this world.