Dear Sir, thank you for your interesting question. First let me apologise for the delay in answearing your quiery, as I was travelling abroad. It seems there are two aspects regarding your question, the legal and the medical one. We procede to this kind of treatment as a last choice, mostly in cases of multiple early miscarriages and biochemical pregnancies, where we cannot determine any obvious (male or female) cause. This cross-over procedure is consider a diagnistic tool in order to compare homologous and heterologous embryos created in different matches (egg donation or sperm donation, or both), that might give us an idea of the causative factor leading to miscarriages. In addition, our legal system does not allow during the same cycle the transfer of gamets to the uterus deriving from diferrent origins (holologous-IVF and eterologous-donation). Therefore it is a diagnostic procedure that can be used only under specific medical advise, but the embryos that would be created could not be transfered all together and mixed up in the same woman in one cycle. Usualy egg-donation embryos are cryopreserved and be usued in a subsequent cycle in the unfortunate event of another miscarriage. Furthermore, it is not medical advisable for the couple to undergo an IVF stimulation and at the end to use egg-donation as the endometrium most of the times in not properly prepared and the pregnancy rates are lower. What is advisable is either an IVF treatment or a gamete donation treatment for better results. Especially for women older than 42yrs, egg donation is probably the most succesfull and therefore most appropriate choice. I hope to have answered your question in detail. Please feel free to email us again, if further specification is needed. Kind Regards.