Purpose: To present a case involving the transfer of a single pronucleated oocyte resulting in a monozygotic twin pregnancy.
Method: A descriptive case report of a single patient.
Results: The patient conceived and was found to have a monochorionic diamnionic pregnancy which resulted in the birth of normal identical twin boys at 32 weeks of gestation.
Conclusions: The case report addresses an issue that has not received proper attention in the literature. It illustrates that observing a single PN in an oocyte at fertilization check should not be an absolute deterrent to transferring the resulting embryo even in an older patient with a high FSH level. This report also suggests that single observations, especially at the assessment of fertilization, in the IVF laboratory are limited when evaluating embryo potential and normalcy.