Blog: Endometrial Receptivity and the ERA assay
21 June 2018
We have seen a bit of online chat lately regarding ERA, so we asked Dr Mary Birdsall, one of our top fertility specialists to write a quick informative blog to help those wanting to know more.
What is ERA?
The lining of the uterus or endometrium goes through some remarkable changes throughout the menstrual cycle. In the first half of the cycle as a follicle grows and produces oestrogen then the lining gets thicker. Once the egg is released from the follicle and progesterone is made by the collapsed follicle (called a corpus luteum), the endometrial cells change to become receptive to implant a developing embryo.
For most women the time of endometrial receptivity for an embryo to implant is accurately predicted by the number of days after ovulation, but for some women the ‘window for implantation’ occurs later or earlier.
The Endometrial Receptivity Assay or ERA is a method whereby the endometrium may be checked to determine whether the date of embryo transfer may need to be adjusted to match the woman’s own window for implantation.
How is it done?
The woman goes through a mock frozen embryo transfer cycle and on the day of embryo transfer instead of replacing an embryo then a Pipelle biopsy is done. This is where a small sample of the lining or endometrium is taken and then couriered to the ERA lab. (For NZ the nearest lab is Japan). The ERA lab then checks the expression of 238 genes in the biopsy sample and sends a report indicating a receptive endometrium or a pre-receptive or post receptive endometrium. The timing of the embryo transfer is adjusted accordingly.
Who should do this test?
The current recommendations are that the ERA may be useful in women with recurrent implantation failure. There is debate about what the definition of implantation failure is, I think reasonable to consider ERA if a pregnancy has not resulted after the transfer of 2 to 3 good quality embryos into a normal uterus, in which the expectation of greater than 80% would have become pregnant.
The ERA group report that women’s results are very consistent month to month, meaning that a woman’s particular implantation window does not change with time or following pregnancy. For 25% of the samples the test shows the time of embryo transfer needs to be adjusted.
This test will cost around $2,800 NZ, this includes the ERA Test Fee, courier costs to Japan, the manufactured cycle and Pipelle biopsy.
Where the result indicates that timing is not ideal, the ERA group recommend another biopsy to check prior to implantation, which does mean an additional cost. Sometimes we may choose just to alter the day of transfer and not retest to save further expense.
The FA experience so far
We have been offering the ERA assay to women with recurrent implantation failure recently. We have seen that most biopsies have indicated that we should adjust the timing of embryo transfer in this particular group of women. We have seen that some women have had ongoing pregnancies but sadly not all.
The Future of the ERA test?
The ERA test is a further step towards personalising medicine and figuring out every individual’s unique make up. I don’t think it is the definitive answer for the black box which is implantation failure. I think it is useful for women with recurrent implantation failure in IVF but not yet for all women not conceiving.