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When mammalian embryos are surgically split (sectioned) prior to converting into a blastocyst, the number of cells and the size of the resulting blastocysts seem to be unaffected. The developmental time clock also remains relatively unaffected. While bisected embryos develop into blastocysts with slightly less than half the number of inner cell mass cells, and slightly more than half the number of cells forming the trophoblast, these alterations do not seem affect the implantation rate of mammalian, non-human embryos. It remains to be discovered whether the same would apply in the case of human embryos.

Several concerns have been raised regarding the production of abnormal offspring and other potential complications that might result from surgically inducing monozygotic twinning through microsurgical embryo splitting (MES). However, it is a fact that in the cattle industry, where MES has been performed successfully for many years, there has to date been not s single report of abnormalities in the offspring.

Microsurgical Embryo Splitting (MES) might ideally be combined with full karyotyping (chromosomal recognition) using comparative genomic hybridization (CGH) on 6-9 cells, day 3 embryo(s) to identify “competent” embryos. This would be followed by MES on day 3 (the cleaved embryo stage of development), or on day 4 (the morula stage). The resulting hemi-embryos so produced would thereupon be cultured for a few days longer to the blastocyst stage when they would either be transferred fresh to the uterus or be vitrified (frozen) and banked for subsequent dispensation. In this manner MES might serve as a means to increase the number of available embryos per woman.Potential complications such as twin-to-twin transfusion, umbilical cord entanglement and obstructed birth, which often occur with natural spontaneous monozygotic twinning, are not encountered in MES-induced twinning. The explanation lies in the fact that unlike natural monozygotic twins that often occupy a single, common gestational sac and frequently share a common blood supply derived from a single placenta, MES-induced monozygotic twins invariably have their own placentas and reside in separate gestational sacs.

MES, should it become a feasible, acceptable and practicable clinical option in ART could by increasing the number of available viable embryos offer hope for thousands of women who because of advanced reproductive age and/or diminished ovarian reserve are only capable of producing very few “competent” eggs/embryos at a time. It might also prove to be of benefit in cases where (out of personal choice) IVF is performed without the use of fertility drugs (Natural Cycle IVF) and where accordingly only one or two eggs/embryos are generated. ———————————————————————-
Addendum: SIRM-Las Vegas is soon to launch a limited study to evaluate the efficacy of MES. Criteria for consideration of inclusion in this study will be as follows: