Received January 07, 2023
Accepted July 21, 2023

Objective: To evaluate the origin and ultrastructure of the coarse perivitelline space inclusions (PVSi) in the oocytes of a group of couples attending assisted reproduction treatment. Methods: The ultrastructure of five oocytes with coarse PVSi obtained from three patients were evaluated by transmission electron microscopy (TEM). The influence of the ovulation induction regimen on the formation of PVSi in 214 couples and the developmental capacity of these oocytes presenting PVSi was analyzed retrospectively. Results: In TEM analysis, the microvilli structure was irregular, short, and loosely scattered through the oolemma in the oocytes presenting coarse PVSi. Furthermore, dense lipid droplets were identified within the PVS and the surrounding cumulus cells. In the retrospective analysis, the number of oocytes with coarse PVSi was positively correlated with the duration of antagonist administration (r=0.23, p=0.013). Independent of inclusion type, the presence of PVSi (moderate or coarse) was positively correlated with low-quality embryos on D3 (r=0.29, p=0.005) and the total number of arrested embryos up to D3 (r=0.33, p<0.001). Furthermore, the presence of coarse PVSi severely exacerbated the abortus rates. Conclusions: Our findings suggest that the presence of especially coarse PVSi is correlated with the reduction of further embryonic developmental capacity in post-implantation stages of embryonic development. This study highlights the negative influence of aggressive ovulation induction protocols on developing oocytes.