Welcome to JA and thanks for this question. Im sorry to hear about your situation. Well you are correct the endometrial lining does continue to thicken until the day of transfer because of the medications that you are on however it is usually not 1 mm per day as that would cause the lining to become too thick. Usually the thickening is around 0.5 mm per day at best (usually it is less than that), in some cases yes it can reach a rate of 1 mm per day. Even if the lining came to be around 16 mm (0.5 mm per day rate) even then implantation should be successful. The problem lies with a too thin lining, anything less than 6-7 mm will make implantation of the embryo very difficult. Yes there are studies which show that a lining thicker than 16 mm MAY cause issues but most of the studies have indicated that the lining should not be too thin, pregnancies can be successful even with thicker lining and the embryo does take hold in linings thicker than 16 mm in many cases.
Usually they wont scan you before implantation as long as your previous scan showed a lining which was greater than 7 mm, because most fertility specialists are more concerned with a thin lining and not a thick one. Studies have indicated that too thick lining is not as big of a factor in implantation failure when compared to a too thin lining.
So in short, the endometrial thickening rate is usually not 1 mm per day, it is usually lower than that and various factors play into the growth rate and secondly given your number of 8 mm 8 days before transfer, i dont believe that the lining would have been too thick for implantation failure to occur.
Do you have any more questions?
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