One of the reasons why Frozen Embryo Transfer or FET cycles have higher pregnancy rates
is because a lot of attention is focused on the optimal preparation of the uterine lining.
When should you NOT go ahead with a transfer of a frozen embryo?
IVF expert Dr. Randy Morris explains in today’s episode of InfertilityTV
In order to prepare the uterine lining so it is receptive to an embryo, it must be exposed
to two different hormones.
The first hormone, estrogen, makes the uterine lining grow thicker.
The second hormone, progesterone, transforms the lining and allows it to develop the ability
to let an embryo implant.
There are a number of different ways that the uterine lining can be prepared.
If a woman ovulates on her own, the estrogen and progesterone both come from the ovary.
Estrogen is produced by the developing follicle before ovulation.
Estrogen and progesterone are produced from the ovary after ovulation.
Commonly, however, doctors have women use estrogen and progesterone medications.
I talk about the different methods in more detail here.
You worked really hard to create your embryos.
You don’t want to waste any by transferring them into a uterus that does not have optimal
conditions.
If an attempt is abandoned before transferring the embryo, fertility doctors call that a
cancelled cycle.
With that background, here are several times in which your doctor may decide to cancel
your embryo transfer
Persistent or heavy vaginal bleeding - It is common to have bleeding in the first few
or several days of estrogen because it takes some time for the uterine lining to grow thicker.
Bleeding after this time, however, is not normal.
It is also not normal after the progesterone has been started.
It is likely ok to have a little bit of light spotting.
Heavier bleeding is more concerning.
What if you have something that is a little bit more than light spotting?
This is a judgement call.
Be sure to mention it to your doctor.
Persistent fluid in the uterine cavity - Sometimes, during the time you are receiving estrogen,
some fluid may be apparent on ultrasound in the uterine cavity.
This is fairly common, it will usually go away on its own especially after starting
progesterone.
At IVF1, if a patient has persistent fluid, we will perform an extra ultrasound on the
day of transfer but early in the morning, before the embryologist has thawed the embryo.
If there is still fluid present after several days of progesterone, we will then cancel
the transfer.
Premature rise in progesterone levels - The estrogen and progesterone prepare the uterine
lining in sequence.
The estrogen acts first and the progesterone acts later.
We have had to cancel embryo transfers when the uterus is exposed to progesterone too
soon.
This happened in one of three situations: 1) The patient has ovulated unexpectedly 2)
The patient inadvertently started taking progesterone before she was instructed to and 3) a slight
increase in progesterone was detected by blood testing . This level of progesterone is too
low to indicate ovulation occurred but it is higher than it should be.
At IVF1, we use a level of 1.0.
It is not known why, in some cases, these small increases in progesterone occur.
Your lining is too thin.
Estrogen is meant to get the uterine to grow thicker.
If it doesn’t do that, it may be reasonable to cancel the embryo transfer.
Recently, however, fertility experts have learned that high pregnancy rates are possible
with thinner uterine linings.
Watch this video for more information about that.
Failure to survive the thaw - not all cancellations are due to problems with the uterus.
Sometimes the embryo does not survive the freezing and thawing process.
The most recent method for freezing embryos called vitrification, or rapid freezing, has
very high survival rates.
The embryo is immersed in solutions that are meant to protect it during freezing.
Despite the use of these solutions, ice crystals can form which damage or destroy the embryo
during the freezing process.
This isn’t recognized, however, until after the embryo is thawed.
This is unfortunate because it means you dont find out until after you have spent weeks
preparing the uterus.
If you are lucky enough to have multiple embryos frozen, then it is possible to thaw an additional
embryo if the first one does not survive and then avoid having to cancel the transfer.
In most cases, if your FET was cancelled, it can still be performed with a future attempt.
In other words, in most cases, the problems that we discussed here can be overcome in
a future attempt