Atypical hatching of a human blastocyst leading to monozygotic twinning: a case report.

OBJECTIVE: To report a case of monozygotic twinning after atypical hatching of a human blastocyst. DESIGN: Case report. SETTING: University-based IVF program. PATIENT(S): A 33-year-old woman with tubal sterility. INTERVENTION(S): Embryo transfer of a human blastocyst with atypical hatching. MAIN OUTCOME MEASURE(S): Development to the blastocyst stage, hatching process, follow-up of pregnancy. RESULT(S): Development of a monozygotic dichorial pregnancy. CONCLUSION(S): First report of an atypical hatching of a human blastocyst leading to dichorial monozygotic twinning.