Background: IVF/ICSI is the preferred treatment option for PCOS-related infertility, however, the risk of ovarian hyperstimulation syndrome (OHSS) is significantly increased.
Aim: Therefore, this study was conducted to estimate incidence and degree of OHSS among PCOS women underwent IVF/ICSI after taking different stimulation protocol in Mansoura fertility unit.
Methods: The study enrolled 108 PCOS cases underwent IVF/ICSI. OHSS occurrence was detected and possible risk factors for moderate to severe OHSS were studied. 
Results: Results revealed that the group of (Antagonist protocol with a GnRH Agonist trigger) had 2.2% OHSS incidence. The group of (Antagonist protocol plus hCG trigger) had an OHSS incidence of 22.6%. The group of (Long Agonist protocol plus hCG trigger) had an OHSS incidence of 25%. The choice of IVF/ICSI protocol (e.g. pituitary suppression protocol, oocyte maturation trigger & freeze all vs fresh embryo transfer) in addition to multiple demographic (e.g. Age & BMI), historical (e.g. LOD), clinical (e.g. AFC), laboratory (e.g. AMH) and follow up (e.g. E2 level at trigger day, Number of follicles ˃18mm, Number of oocytes retrieved, Number of transferred embryos, Clinical pregnancy, multiple pregnancy) factors affected OHSS incidence significantly. 
Conclusion: To reduce the likelihood of Ovarian Hyperstimulation Syndrome (OHSS) occurring, certain measures can be taken, including employing the GnRH antagonist protocol for inhibiting the pituitary gland and Stimulating ovulation through the use of a GnRH agonist, as well as cryopreservation of all embryos (IVF/ICSI cycle segmentation). Close monitoring of PCOS patients during IVF/ICSI with treatment plans individualization.