Objective: To report an interesting incidental occurrence that may improve the understanding of the mysterious embryology of conjoined twins.
Methodology: The embryos were generated in-vitro through intracytoplasmic sperm injection ICSI. On day 3 of embryo development, the Zona of each 8-cell embryo was breached with LASER and the embryos were cultured in pairs per well in a culture dish in preparation for herniation for a day 5 trophectoderm biopsy for Pre-Implantation Genetic Diagnosis.

Results: On day 5, a particular pair of embryos was accidentally placed at very close proximity adjacent to each other. Interestingly, during herniation, the trophectoderm cells were observed to have joined and started developing together into “conjoined embryos”.

Conclusion: The fact remains that there are more mysteries surrounding the origin or the embryology of conjoined twining. The current knowledge is that of two theories postulated of which the fission theory is the most widely accepted. This finding could support the fusion theory.

Keywords: Trophectoderm; Fission theory; Conjoint embryo; Mysteries

Full Abstract Case Report on “Conjoined Embryos”