Influence of corifollitropin alfa on embryo morphokinetics and fertility treatment outcome

Background Corifollitropin alfa (CFA) is a long-acting recombinant follicle-stimulating hormone that reduces injection burden during controlled ovarian stimulation (COS). While its clinical efficacy has been demonstrated, its potential influence on early embryo development assessed by time-lapse morphokinetics remains insufficiently explored. Methods This retrospective cohort study analyzed embryos derived from COS using either CFA or daily follitropin β. A total of 561 embryos from 99 CFA-stimulated patients and 3,116 embryos from 481 follitropin β-stimulated patients were included. Embryos were cultured in a time-lapse incubator, and morphokinetic parameters including pronuclear fading (tPNf) and early cleavage stages from t2 to t8 were recorded. Linear mixed-effects models were applied to account for repeated measurements per patient. Clinical outcomes including fertilization, biochemical, clinical and live birth rates were compared between groups. Results Patients receiving CFA were older and showed lower anti-Müllerian hormone levels and higher baseline FSH concentrations, indicating a reduced ovarian reserve. No significant differences were observed between groups in morphokinetic parameters, including cleavage timings (t2–t8), cleavage synchronicity, or early developmental progression (all p > 0.05). The numbers of retrieved oocytes, metaphase II oocytes, and fertilization rates were comparable between stimulation protocols. Biochemical pregnancy rates were lower in the CFA group; however, clinical pregnancy and live birth rates did not differ significantly between groups. Conclusions Controlled ovarian stimulation with CFA does not appear to affect early embryo morphokinetics as assessed by time-lapse imaging. Despite differences in baseline patient characteristics, CFA was associated with comparable embryo developmental dynamics and live birth outcomes compared with daily follitropin β stimulation. These findings suggest that CFA may represent an alternative COS strategy in routine clinical practice without apparent detrimental effects on early embryo development; however, they should be interpreted with caution due to the observational design.