Rescue oocyte retrieval efficiently recovers the oocyte from earlier ruptured follicles in controlled ovarian stimulation

Earlier follicle rupture or ovulation after trigger in controlled ovarian stimulation (COS) is still not uncommon even under close monitoring and tight luteinizing hormone (LH) control. We explored the efficacy of rescue oocyte retrieval (ROR) in recovering the oocytes from earlier ruptured follicles. In a single private practice, 83 cases of COS with earlier ruptured follicle(s) before the scheduled oocyte retrieval time were included from September of 2020 to March of 2023. The follicles without earlier rupture in the same COS cycle or other similar COS cycle without earlier ruptured follicle of the same patient were matched as the control group. To recover the oocytes from earlier ruptured follicle, ROR was attempted first in the capsule of the ruptured follicle(s). If no capsule could be identified or no oocyte was recovered from the capsule, pelvic free fluid was collected for searching the oocyte. Student T test and ANOVA were applied to analyze the data. Of the 83 cases, the reasons for earlier ruptured follicle after trigger include uncontrolled LH pre-surge (51.9%), late presentation for scheduled oocyte retrieval procedure (12.3%), unknown (35.8%), and others (2.5%). There was no significance difference in the patients' age (41.17±5.9, 41.1±6.0, 42.7±4.2, and 41.6±4.5 YO) and BMI (25.8±6.5, 28±5.3, 25.93±6.3, and 27±5.9) upon oocyte retrieval. Of the 115 earlier rupture follicles, 49 (42.6%) oocytes were recovered comparing to the 92 (87.6%) oocytes from 105 non-ruptured follicles (p<0.00001). Forty oocytes were recovered from 90 follicles ruptured before entering operative room (OR) and 9 oocytes from 25 follicles ruptured in OR (p=0.45). Of the 49 oocytes obtained from successful ROR, 22 were recovered from the capsules and 27 were recovered from the free fluid in pelvis. Among the oocytes from the ROR group and the control group, the only significant difference was in the fertilization rate of mature oocyte (70.4% vs 92.5%) (p<0.01), while the oocyte maturity rate (97.8% vs 97.8%), cleavage rate from fertilized oocytes (94.7% vs 95.8%), blastulation rate from cleavage embryos (37.5% vs 75%) after fertilization showed no significant difference. One healthy baby was delivered from the embryos created from 3 oocytes recovered by ROR, while there was only 1 chemical pregnancy from 4 oocytes in the control group. Due to the co-culture of the oocytes from earlier ruptured follicle and non-rupture follicle retrieved at the same time in most of the cases, fertilization rate and embryonic development could not be fully investigated among all the eggs recovered from ROR. Oocyte could be recovered from pelvic free fluid as well as ruptured follicle capsule for earlier ruptured follicle by ROR. Except for low fertilization rate, there was no significant difference in cleavage rate and blastulation rate after fertilization between oocytes from earlier ruptured follicle and non-ruptured follicle.