Ask the Surrogacy Experts

We are having trouble deciding on transferring one or two embryos. We would like your thoughts. This will be our first transfer attempt, and the clinic gave us some recommendations but we don’t really know how to interpret them. We hope to have a boy. We would also be OK with two boys or a boy and a girl, but we’re worried about having twins. Mostly because we hear that twins have a high chance of premature birth (60% or more) and weeks in the NICU. –Jeremy


Hello Jeremy.

In the United States IVF clinics are required to report all IVF cycles and their outcomes. The results for a de facto ranking of IVF clinics by success rates, and can be viewed on a few different online portals. Among the data is stats on clinics that transfer one or two embryos.

The results of the data are not what you might expect. The clinics with the highest success rates are overwhelmingly those that transfer only one embryo at a time. After perusing the reports on IVF clinics across the US, those that are more amenable to transferring 2 embryos have success rates far below their counterparts.

Specifically, of the 10 top ranked IVF clinics nationwide, the median Live Birth rate using donor eggs was 62.9% with an average of 1.2 embryos per transfer. Compare that with the clinics ranked from 20 to 30, which have a Live Birth Rate of 60.5% using 1.6 embryos per transfer. In the comparison, the top ranked IVF clinics use fewer embryos in each transfer.

Now, this could be for a number of reasons… For example it could be that the most successful clinics are more likely to be working with healthy donors and surrogates. It could also be that high-ranked clinics more strictly follow the ASRM guidelines.

But regardless of the specific reasons, the data clearly indicates that there is no sign that transferring more embryos will get you a higher likelihood of a pregnancy.

As always, I would defer to your doctor’s judgement when deciding how many embryos to transfer. There are always qualifying circumstances that will push you in one direction or another. Only your doctor is aware of those circumstances.

But that said, my experience is that transferring two embryos does not drastically increase the likelihood of a pregnancy, but it does drastically increase the likelihood of a twins pregnancy. If you want to avoid a twins pregnancy, then you should transfer one embryo at at time.

Yes, twins pregnancies have a high occurrence of premature birth. (More on that at this article in the Guide.) Twins pregnancies are also hard on the surrogate and she’ll require additional support during the pregnancy, it’s very possible she’ll need extra medical care — You mentioned your surrogate has a history of kidney problems, and I suspect twins would exacerbate that.

Also, there are studies that show that if you transfer two embryos of unequal developmental quality, the lower quality embryo will lessen the likely success of the more healthy embryo. (There are medical reasons for this, which I won’t go into.) So if you transfer two, don’t transfer your best along with your worst. The studies suggest that two transferred embryos should be about the same quality.

I think if you are not determined to have twins, the likelihood of a healthy pregnancy is higher with 2 transfers of 1 embryo each, rather than 1 transfer of two embryos. If you do want to have twins, transfer your two highest quality embryos, and then prepare the surrogate for a harder than normal pregnancy.

I hope this make sense and is helpful.
— Bill


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