ERA - Receptivity Testing Results
8/24/23
Exactly 2 weeks ago, I had an ERA (endometrial receptivity array) performed. As I noted in my article, Planning for ERA and FET, the purpose of the ERA is to determine exactly (down to the hour) when your uterine lining is most receptive to receiving and holding onto an embryo.
The process of an undergoing the ERA test is to go through an ERA cycle, which is essentially exactly the same as a Frozen Embryo Transfer (FET) cycle except that instead of transferring an embryo, they perform a biopsy and take a sample from your uterine lining to test it’s receptivity. The results of the ERA test give you 2 important pieces of information:
Whether you ARE or ARE NOT receptive (to embryo implantation)
A number - this number tells you your ideal transfer window - the number represents the exact number of hours you should be on progesterone prior to the embryo transfer in order to have the highest rate of success for embryo implantation (wow!)
Two weeks ago, when my ERA test was performed, I was advised results could take 2.5-3 weeks. However, to my surprise the results came back early and my doctor called me today! She shared with me the 2 important pieces of information:
I was receptive (yay!)
My score was 132
Of course, I was thrilled it showed receptive. Non-receptive could mean undergoing another ERA cycle - No thank you!
The more valuable detail and the real purpose for me undergoing the ERA was to find out my receptivity window. As I mentioned, 132 means 132 hours is the ideal amount of time my body personally needs to be on progesterone before my uterine lining is most receptive to implantation. There is a “receptivity window” that is 3 hours +/- 132. Meaning 129-135 hours.
My doctor shared with me that the average person requires about 120 hours. This was the amount of time I was given between the start of progesterone and my ERA. It was also the window of time I was on progesterone when I had my failed FET.
I won’t say I was “excited” about this news but it did give me an answer! There is a high likelihood that my FET failed because I wasn’t on progesterone for long enough and my uterine lining just simply wasn’t ready and receptive to implantation. Had we waited another 9-15 hours, it just might have worked. Having this piece of information is so powerful. Now we can go into our FET cycle with greater confidence in our timing. I love that!
Another detail she shared with me was a comparison between the embryo transfer we did on my successful FET when I became pregnant with Mila back in 2020. Following the egg retrievals (2) and the fertilization to create our embryos, we froze all of our embryos so they could undergo testing and I could prepare my body for the embryo transfer. After 2 egg retrievals (52 eggs retrieved) we wound up with only 3 viable embryos. The “best” of the 3 was used for our first transfer.
Now, since the embryos were all frozen, the embryo they planned to transfer had to first be thawed and then hatched (you pay extra for hatching - yay!).
Quick science lesson: an embryo has an outer shell called the zona pellucida. The embryo must break out of this shell and “wake up” before it’s ready to implant into the uterus.
By using assisted hatching, we had the embryologist essentially break the outer shell (zona) making it easier for the embryo to fully hatch and “wake up” so it wasn’t left to do this on it’s own. In most cases with assisted hatching, the embryo will not be fully hatched by the time the doctor performs the embryo transfer. The remainder of the hatching will occur while inside the uterus. However, when they performed the assisted hatching on our embryo - it fully hatched before the embryo transfer occurred (and ultimately it was a success!).
The doctor informed me that there is a reason they don’t purposely fully hatch embryos prior to transfer every time and that is because it slightly increases the likelihood of the embryo splitting and becoming identical twins. However, the likelihood of this happening is still only about 1 in 1,000.
When we looked at the embryo that was transferred back in May, the assisted hatching was performed but the embryo did not fully hatch. So along with the high potential of an incorrect receptivity window, there was also the potential of delayed timing of the embryo hatching. The bummer with this detail is that you can never know exactly how long the hatching took and it can vary across embryos so it’s not a factor you can pin down during a transfer.
So although we were probably many hours off on the receptivity window during that transfer and the timing of hatching likely didn’t matter, embryo hatching time does become a consideration when we’re looking at timing everything exactly. If the embryo is not fully hatched and the transfer is performed at the ideal time during the receptivity window, you still run the risk of the embryo taking too long to finish hatching and then “waking up” before it attempts to implant into the uterine lining, leading to a failed transfer.
Our doctor offered us two options:
Perform the assisted hatching and hatch it all the way - with the minimal risk of identical twins. When the embryo is transferred, it’s already ready and awake and can seek out the uterine lining and implant.
Perform assisted hatching but don’t hatch it all the way and allow it to finish hatching in the uterus. With this option, she would plan to transfer maybe even 1-2 hours before the receptivity window to allow the embryo another 1-2 hours to fully hatch in the uterus before the clock starts ticking on the receptivity window.
This has certainly left us with something to think about. Although the likelihood of identical twins is very minimal, it would not be something we’re interested in (in any way shape or form) so we have to consider that risk. Additionally, at my age (39) an identical twin pregnancy is a high-risk pregnancy and can cause complications - another thing we have no interest in! At the same time, we’ve already transferred a fully hatched embryo in the past and everything was just fine! And a fully hatched embryo is a guarantee that it’s ready for finding its home in the uterine lining during the receptivity window, which is a HUGE benefit. So yes, we have things to think about.
Prior to my ERA, I was really clueless to this whole process and what it all meant. I truly hope that by sharing some of the details of our ERA cycle and the results, you feel a little more well-informed and able to make decisions about whether an ERA is a good option for you or how it may benefit you. As I always say, I truly enjoy connecting with people who are going through their own fertility struggle and being a safe place of empathy, support, guidance, and understanding for my fellow fertility fighters! If you’re going through your own fertility journey now and need someone to connect with, don’t hesitate to reach out. Most people have been DM’ing me on Instagram.
