Deep Dive

The Risks and Benefits of Single and Multiple Embryo Transfer

How many embryos you have transferred impacts the rest of your life. This is a complex, and crucial decision, because increasing the number of embryos may shorten your time to success, but also ramps up the risk to you and your offspring. When we surveyed over 400 IVF patients on the subject, we learned their doctors told them dramatically different things, and over 20% only had this discussion just before transfer, so let’s try and level-set on the facts ahead of time.

The Risks of Multiple Embryo Transfer


When you transfer more embryos in a transfer, the risk rises that you will have a multiple pregnancy. Let’s look at Sweden: they did away with multiple-embryo transfer and now they have almost exclusively singletons born from IVF.

The notion of twins may be endearing, but giving birth to them can be incredibly dangerous. As you can see below, the risk of labor complications and infant mortality shoots up, nearly 5x.

In fairness, these absolute percentages may seem small to some, but carrying multiple fetuses leads to premature-birth, and low-birth weight, in 57% of cases for twins and 97% of cases for triplets. Nearly a third of all twins will end up in the NICU.

Why does that matter? For one, low-birth weight and premature offspring suffer from significant emotional and cognitive disadvantages. JAMA investigated 18 studies on the subject and all 18 agreed.

When we surveyed over 400 IVF patients who had the option of doing a single or multiple-embryo transfer, we discovered patients weren’t learning these facts. Or if they did, they had no recollection. 39% of patients were not educated on the risk to the offspring and 23% were not educated on the risk to themselves. And yes, as you can see below, this impacted whether they decided to transfer one or multiple embryos.

The Benefits of Multiple Embryo Transfer


For many patients, they will take on all of this risk if it raises their chance of having a child. Let’s break this down into two parts:

Baby Faster: Does multiple-embryo transfer get you a baby in shorter time.

Baby Eventually: Does multiple-embryo transfer raise your chances of getting a baby, regardless of time.

Baby Faster


When you transfer multiple embryos in a single transfer, by and large, you are more likely to have a child than if you did one transfer with a single embryo. But this is only true up to a point.

When the CDC and the University of Iowa looked at the issue, they noted the woman’s age and the number of embryos she had available were critical factors.

When women were under 35 and had up to three embryos available, they had similar rates of success when they transferred multiple embryos, or a single embryo, in the first transfer. But when these women had four embryos, the multiple-embryo transfer group had higher rates of success in that first transfer.

When they looked at women ages 35 – 37, the data shifted so that only women with two embryos had similar results, otherwise the advantage went to women doing a multiple-embryo transfer. And this speaks to a trend: generally speaking, multiple-embryo transfer tends to benefit older patients more than it benefits younger patients.

That wisdom has held until the broader use of PGS. One study from a single center (which can only be so representative) noted that success rates were equal for women transferring a single PGS-tested embryo and women transferring multiple non-PGS tested embryos. And that applied to women up through age 42.

From our own data we have noticed that patients who have had their embryos PGS-tested are far more likely to elect to transfer one embryo at a time than multiple embryos in a single transfer.

Baby Eventually


Patients who elected to transfer a single embryo have unused embryos they can transfer if their first transfer fails. When we take the success rates for the single-embryo transfer group, and add to them the success rates of those who failed from this group but then did a second transfer with an excess embryo, we notice this group as a whole has similar success rates as the group who did a single, multiple-embryo transfer. So, in theory, whether you transfer two embryos at once, or a single embryo twice, you are just as likely to take home a child. Atleast for women up through ages 36.

Patient Fatigue


However, that is “in theory” because it assumes the patient has the money, time and wherewithal to return after a failed transfer. For one, each additional transfer costs about $3,000 and for some they cannot afford the extra cost. However, we believe many, many patients may confuse the cost of an extra transfer for that of another cycle, which is $23,000).

For another, every transfer exacts a temporal and emotional toll on the patient. The fear of bad news can be crippling and for that reason the IVF “drop out” rate is high. Simply stated, many of us run out of emotional stamina before we run out of money.

Our survey data shows that when patients are more educated that multiple-embryo transfer is less likely to require a second transfer, they are far more likely to opt for it versus single-embryo transfer.