Abstract
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.