Related Experiment Video
Updated: Jun 18, 2025

Fertility Preservation Through Oocyte Vitrification: Clinical and Laboratory Perspectives
Published on: September 16, 2021
The dark side of random-start ovarian stimulation: ovarian hyperstimulation syndrome due to inadvertent pregnancy
N Semrl1, M De Vos2, C Blockeel2
1Department of Obstetrics and Gynaecology, Medical University of Graz, Graz, Austria; Brussels IVF - UZ Brussel (Centre for Reproductive Medicine), Brussels, Belgium.
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.
Related Concept Videos
Oogenesis
Ovarian Cycle
Hormonal Control of the Ovarian Cycle
Before puberty, the hypothalamus releases GnRH in a low frequency, low amplitude pulsatile manner. This along with the immature hypothalamic-pituitary-gonadal axis activity, results in low estrogen levels and the absence of a fully functional ovarian cycle. At puberty, GnRH secretion increases in both frequency and...
Meiosis II
Meiosis vs. Mitosis
Before the start of mitosis and meiosis I, the cell synthesizes DNA, resulting in two homologous copies of each chromosome. DNA synthesis is...

