The ERA or Endometrial Receptivity Array has emerged as an important test
for maximizing IVF success. When should IVF patients consider having it done? Stay tuned.
What is the ERA? The ERA or endometrial receptivity array is a test
used to determine whether a frozen embryo is being transferred at the
correct time. The uterus needs two hormones to prepare for implantation.
The first hormone, estrogen, works to thicken the uterine lining. The length of time
that a woman takes estrogen does not seem to be important. Whether longer or
shorter, the chance for pregnancy doesn't seem to change - as long as the lining
gets thick enough. The second hormone, progesterone, causes changes in the
uterine lining that allow an embryo to implant. These changes don't occur
immediately, however. It takes several days before the uterine lining develops
the capacity for allowing an embryo to implant. The uterus only maintains this
ability for a short time. This is known as the "window of implantation".
If an embryo is placed into the uterus before or after the window of implantation,
it has a lower ability to implant and produce a pregnancy. Stated another way
for an embryo transfer - Timing is Everything! How is the test performed?
Doctors will have their patients perform a "mock cycle". In a mock cycle, women take
the same medications that she would take during a transfer cycle: estrogen
followed by progesterone. Then, instead of doing a transfer, the doctor takes a
small sample of the uterine lining. This is called an "endometrial biopsy".
The testing is done on this sample. What do the results mean? When the results are
received, they will indicate that the timing was correct, this is called
"Receptive" or that the timing was incorrect, which is called "Non receptive"
The non receptives can be further divided into two groups: "Pre-Receptive" means
that the lining needs more time before it is ready and "Post-Receptive" means
that the lining was already past the time of maximal receptivity
and therefore needs to be shortened. If the results are pre or post
receptive, the testing lab will also give a recommendation for how to change it.
For example, if the biopsy was performed 125 hours after progesterone was started
and was "Pre-Receptive", the recommendation might be to perform it 24 hours later at
149 hours. For most women, the window of implantation occurs on the sixth day of
progesterone. When does it make sense to do the test? Couples who have never
failed an embryo transfer have a low chance for finding an abnormal result.
Somewhere around 5 to 10%. In other words, more than 90% of the time, couples
without any previous failures will not benefit from doing the test. Studies tell
us that couples who have failed to achieve pregnancy after multiple
attempts at embryo transfer, with high quality embryos, have a higher chance for
continued failure with additional attempts. The first group that might
benefit from an ERA are those that have had multiple failures.
Studies show that in couples with multiple failures, about one third will
have an abnormal test. Couples with a non-receptive result that don't make any
changes to the timing, will have a lower chance for success if they try another
embryo transfer. Another group that seems to have a higher chance for an abnormal result
are women who are obese. Fertility doctors designate patients with obesity
as those women with a BMI or body mass index over 30. Women with a BMI over 30
have the same rate of abnormal results as couples with multiple failures.
Women with a BMI over 40 have an even higher rate of abnormal test results. One group
One group of patients that I get asked about frequently are those with early miscarriage.
In this group, implantation of the embryo occurred, but there was a
miscarriage in the first several days before a pregnancy could be seen on ultrasound.
Some people thought that this could be the result of placing the
embryo at a less than optimal time outside the peak window of implantation.
However, the studies so far do not show a benefit of
using the ERA in this group. Our InfertilityTV bottom line is this: Women
with multiple failures should consider having an ERA before their next transfer
and women with a high BMI should consider having the ERA before
their first transfer. The ERA is designed to benefit couples who have not
had first-time IVF success. If you are looking for tips for first-time IVF
success, check out this playlist. If you like this video like this video.
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