Complex sentence: This is probably important in order to limit the exchange of migratory cells between the developing embryo and the body of the mother, as some blood cells are specialized to be able to insert themselves between adjacent epithelial cells.
Split into simpler sentences: This is probably important in order to limit the exchange of migratory cells between the developing embryo and the body of the mother. Some blood cells are specialized to be able to insert themselves between adjacent epithelial cells.