Why do women who miscarry blame their uterus?
Many infertile women feel that it is their uterus which is defective when they miscarry. This is a misconception which needs to be corrected !
I often see women who have had recurrent miscarriages, or who have failed many IVF cycles, who want me to do surrogacy treatment for them. From a purely rational point of view, this makes perfect logical sense . Their reasoning is simple - the fact that they are getting pregnant means that they are fertile; and the fact that the embryo is growing well within the uterine cavity for eight weeks and then not developing any further, clearly means that there is no problem with the embryo. Their unstated hypothesis is that their must be something wrong with either their uterus or the ability of their body to nourish the embryo after 8 weeks, as a result of which their embryo dies in utero and does not develop any further. It makes perfect sense for them to feel that their body is " rejecting " the embryo - perhaps because of some unexplained biological reason, which doctors still do not have the technology to be able to detect . If this hypothesis is true, then it makes sense to them to transfer their embryos into another woman's uterus, where they will not be rejected, so that they can grow and become a longed-for baby.
This hypothesis is based on assumption that when a miscarriage occurs at 10 weeks, this happens because the uterus is defective. I agree this makes sense - after all, if the embryo developed within the uterus uneventfully for up to eight weeks, doesn't this clearly establish the fact that the embryo must have been perfectly fine? After all, if the embryo could continue to grow normally up to eight weeks, doesn't this imply that the embryo was normal? After all, if it hadn't been normal, would it even have been able to implant in the first place ?
This hypothesis is flawed. A number of studies have proven that the commonest reason for a miscarriage is not a problem with the uterus, but rather problem with the embryo. There are many conditions in which the embryo is chromosomally abnormal or genetically defective, but will continue to develop normally upto 8-10 weeks. These defects become apparent only after the passage of time, so that though the embryo develops and divides uneventfully until it reaches about eight weeks, it cannot develop any further because of the lethal genetic defects which it carries. Conceptually, one could think of this as being nature's defense mechanism, which prevents the birth of abnormal babies.
This fact has been established beyond any doubt. Chromosome studies done on products of conception after a miscarriage show that over 70 percent of them will be genetically abnormal; and even those which are apparently genetically normally, may have subtle genetic defects which we still cannot pinpoint today.
Medical students are taught this simple rule - if you hear hooves, you think of horses - not zebras. Common things occur commonly - and if you have had a miscarriage, the probability that there is something wrong with your embryo is far greater than the chance that there's something wrong with your uterus. This is why the success rate of using donor eggs and donor embryos for patients with recurrent miscarriages or multiple failed IVF cycles is so high. This is especially true for older woman, who have a much higher risk of having genetically abnormal embryos because their eggs are older .