Identifying risk factors related to monozygotic twins after assisted reproductive technologies

Abstract Objective This secondary analysis aimed to identify the incidence and risk factors associated with monozygotic twins (MZTs) after assisted reproductive technology (ART). Study design In this retrospective cohort observational study, the treatment cycles were compared between MZT and non-MZT pregnancies using logistic regression analyses. Of the 11,501 patients with 13,225 pregnancies, 166 MZTs were diagnosed (1.44% in ART pregnant patients; 1.25% in pregnant cycles). Results Results of the logistic analysis revealed that embryo stage at transfer and number of good-quality embryos were independent predictive factors for MZTs. The thresholds for two factors were 3.5 and 3.5. The efficacy of embryo stage at transfer and number of good-quality embryos for MZTs were evaluated using receiver-operating characteristic curves. The areas under the curve (AUCs) for these two parameters were 0.708 and 0.633, respectively. Adding number of good quality embryos increased the discriminative ability of the model (AUC = 0.745). Conclusions The incidence of MZTs, subsequent to ART, is quite high. Extended culture (≥3.5 days), together with the number of good-quality embryos (≥3.5), conferred the greatest risk of producing MZTs.