Monozygotic twins in infertile patients with advanced maternal age: case reports and review of the literature

Objective To report two cases of successful monozygotic twin pregnancies in women undergoing infertility treatment and to review possible etiologic factors. Design Case report and review of the literature. Setting University of Toronto–affiliated infertility clinic. Patient(s) A 43-year-old woman and a 44-year-old woman with history of secondary infertility. Intervention(s) In vitro fertilization and ET. Main Outcome Measure(s) Monozygotic twin pregnancy. Result(s) Delivery of two sets of monozygotic twins. Conclusion(s) The only identified potential risk factors for monozygotic twins are maternal age and assisted reproductive technologies. Both patients reported here were aged >40 years and underwent assisted reproduction procedures, including high-dose gonadotropin stimulation, embryo culture, and, in case 2, intracytoplasmic sperm injection plus assisted hatching.