In the past, in order to boost the chance for pregnancy, IVF programs would put multiple
embryos into the uterus at the same time. This resulted in many pregnancy complications due
to the large number of twins and triplets. Success rates from IVF have improved over
the years. What are the risks and benefits of transferring one or more embryos today? Stay tuned
In 1995, if you were a good prognosis patient under the age of 35,
doing an IVF cycle in the United States, the average number of embryos that were transferred
at one time was 4! By 1999, the average number of embryos transferred had dropped to 3.
By 2009, it was 2. Today, it is just over 1 embryo at a time.
What has happened to IVF pregnancy rates during that time? They have actually increased! With
improvements in IVF technology, doctors discovered that they could transfer less embryos and get
the same or a higher number of pregnancies. This had a dramatic benefit in reducing the
number of multiple pregnancies. In 1995, over 30% of IVF pregnancies were twins. Now it is
less than 10%. In 1995, 5% of IVF pregnancies were triplets. That number is now less than 1%
Why are IVF doctors so interested in reducing multiple pregnancies? The reason is simple.
Multiple pregnancies have more complications and a higher chance for bad outcomes. What
kind of bad outcomes? Compared to a single baby, twins are 6 times more likely to be born preterm,
5 times more likely to end up in the neonatal intensive care unit and four
times more likely to have cerebral palsy. They are also more likely to be stillborn,
die in the first month after birth and have birth defects.
At the same time, IVF doctors and patients would like to get a healthy live born baby with as
little work as possible. Here is a common question that IVF doctors get asked today.
If you have two embryos to transfer, is it better to put both in at the same time?
Or is it better to transfer one and then if needed, transfer the second one later.
We can answer this question using data from the U.S. IVF registry. All IVF programs in
the USA are required to report their IVF outcomes to this registry. For each attempt,
we report many variables including how many embryos were transferred,
what stage the embryos were at, and whether a pregnancy or live birth occurred.
Since most top IVF programs transfer embryos at the blastocyst stage,
we will look at that data. In 2018, for those people who had transfer of two blastocysts,
the chance for having at least one live born baby was 60%. 27% of the pregnancies were twins.
However, people who transferred one blastocyst and then if they didn’t have a live birth transferred
another single blastocyst did better. In this case, 66% of the patients had
the birth of at least one baby but the chance for a twin pregnancy was only 1%.
How is this possible? The math works because although you may
get a few more people pregnant initially by transferring two embryos at the same time,
more of those pregnancies are lost due to complications
such as miscarriage or preterm delivery so that you actually have less live births.
Our InfertilityTV Bottom line is this. In 2022,
your best odds for having a healthy live born baby is to transfer one blastocyst at a time