Three blastocyst stage embryo transfer resulting in a quintuplet pregnancy.

High-order pregnancies are associated with high morbidity and mortality and the incidence is increased as a drastic complication of assisted reproductive technology. This case presents a high-order pregnancy achieved by transfer of three blastocyst stage embryos resulting in a quintuplet pregnancy including a monochorionic triplet. Following the selective termination of the monochorionic triplet, two healthy children were born. The mechanism of monochorionic development and its association with assisted reproductive technology are discussed.