Multi-nucleation of human embryos: clinical and laboratory factors in its occurrence and its impact on developmental capacity

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OBJECTIVE: Multinucleation, the occurrence in embryos of blastomeres with ≥ 2 nuclei per blastomere, can be a criterion for exclusion from transfer in In Vitro Fertilization (IVF). Clinical and laboratory factors that may influence the occurrence of multinucleation were considered. DESIGN: Retrospective review of clinical profiles of patients with embryos in which 0 % (control) or ≥50% multinucleated blastomeres (MNB-emb) were identified on Day 2 of development, and the prospective study of morphology and implantation of the embryos from these two groups. MATERIALS AND METHODS: Two groups of patients in a continuous interval from January to May 2007 were studied: those having no MNB-emb (control, n=267) and at least one MNB-emb (n=206). These patients were compared for age, BMI, day 3 FSH, type of pituitary suppression and ovarian stimulation, mean estradiol (E2) at time of hCG, days of stimulation, number of eggs retrieved, and pregnancy rate. The incidence of MNB-emb was compared according to method of fertilization (insemination or ICSI), and the morphologic quality of the embryos from both groups was assessed. RESULTS: No significant differences were observed between control and MNB-emb groups with respect to age, BMI, day 3 FSH, mean E2 at hCG trigger, number of eggs or days of stimulation. Ovulation induction protocols were similar in both groups. Method of fertilization did not influence the incidence of MNB. Significantly more embryos with good morphology were found in the control compared to the MNB-emb group at day 2 (41.8% vs. 38.5, respectively, p=0.001) and day 3 (30.5% vs. 25.3%, respectively, p=0.01). While the number of embryos transferred in the MNB-emb group was significantly higher than the control (2 vs. 1.7, respectively, p=0.05), there was no difference in the implantation rates (30.3% vs. 31.2%, respectively). CONCLUSIONS: These findings demonstrate that the occurrence of embryos containing multinucleated blastomeres in a cohort does not reflect a reduced developmental capacity of the sibling non-multinucleated embryos. Further, the occurrence of MNB-embryos cannot be predicted on the basis of the patient factors or treatment cycle dynamics examined in this study, and may reflect gamete- or embryo- specific cellular deficiencies or anomalies.