The dark side of random-start ovarian stimulation: ovarian hyperstimulation syndrome due to inadvertent pregnancy

Research question: Can inadvertent pregnancies go unnoticed when initiating random-start ovarian stimulation (RSOS) despite monitoring? Design: Case series at a university-based tertiary care fertility clinic. Results: Between June 2022 and December 2023, two cases of undetected early pregnancy at the onset of RSOS were identified, both leading to severe ovarian hyperstimulation syndrome (OHSS) with hospitalization. Conclusion: RSOS protocols add flexibility in fertility clinics when there is no intention of a fresh embryo transfer, but may be associated with insidious risk of OHSS. The authors advocate for comprehensive consultation and serial monitoring of human chorionic gonadotrophin during ovarian stimulation, while cautioning against over-reliance on baseline hormone concentrations when initiating RSOS. If the benefits of RSOS seem limited, healthcare providers should consider delaying ovarian stimulation to avert health, but also medicolegal and financial, complications.