Effect of GnRH analogues for pituitary suppression on oocyte morphology in repeated ovarian stimulation cycles

OBJECTIVE: To compare the effect of pituitary suppression regimens on oocyte morphology in consecutive ICSI cycles of the same patients. METHODS: Data was obtained from 200 matched consecutive intracytoplasmic sperm injection (ICSI) cycles performed in 100 couples undergoing the first cycle with the GnRH agonist and the following cycle with the GnRH antagonist regimen, from January 2010 to August 2016, in a private university-affiliated IVF centre. The effects of the pituitary suppression type on oocyte morphology were assessed by multivariate General Linear Models. RESULTS: Mean interval between cycles was 185.32±192.85 days. Maternal age, body mass index, and total FSH dose administered were similar in both patients' cycles. Antagonist cycles presented lower incidence of dark cytoplasm (0.69±3.28% vs. 4.40±17.70%, p=0.047), Smooth endoplasmic reticulum (SER cluster (4.37±11.62% vs. 7.36±17.17%, p=0.046), and ZP defects (6.05±14.76% vs. 11.84±25.13%, p=0.049). Similar numbers of follicles retrieved oocytes, and mature oocytes were observed between the GnRH groups, as well as the fertilisation rate, number of obtained embryos, high-quality embryo rates, and the clinical outcomes. CONCLUSION: GnRH antagonist's inhibitory effect on the ovaries in consecutive ICSI cycles results in improved oocyte maturity and morphology, despite similar laboratory and clinical outcomes, compared to the GnRH agonist treatment.