Herniated blastomere following chemically assisted hatching may result in monozygotic twins.

OBJECTIVE

To explore a possible mechanism of the increasing incidence of monozygotic twins following assisted hatching of human embryos.

DESIGN

Case report.

SETTING

Clinical research center in a medical school teaching hospital.

PATIENT: A 37-year-old infertile woman with repeated IVF failures.

INTERVENTION(S): Assisted hatching of the day 3 embryos using acidic Tyrode's solution.

MAIN OUTCOME MEASURE(S): The morphology of the zona-drilled embryos and the pregnancy outcome.

RESULT(S): After assisted hatching, a herniated blastomere through an oversized opening in the zona pellucida was found in one embryo. The transfer of two zona-drilled embryos resulted in a triplet pregnancy.

CONCLUSION(S): Large openings in the zona pellucida following chemically assisted hatching may cause premature hatching of the blastomeres and may be implicated in the occurrence of monozygotic twins.