Effect of Nitrous Oxide During Oocyte Retrieval on In Vitro Fertilization Outcomes: A Retrospective Study

Background Nitrous oxide (N₂O) is commonly used during general anesthesia for ovum pickup during in vitro fertilization (IVF) cycles. N₂O deactivates methionine synthetase, thereby reducing the amount of thymidine available for DNA synthesis in dividing cells, which might be the reason for the low implantation rate or increased frequency of early pregnancy loss. The aim of this study is to find out the IVF outcomes after exposure to either isoflurane or a combination of isoflurane + N₂O during anesthesia administration in the oocyte retrieval procedure. Methods This retrospective analysis was conducted on 250 patients undergoing IVF procedures who received anesthesia with isoflurane + N₂O or only isoflurane. Medical records were obtained for patient data, anesthesia details, and IVF outcomes. The primary objective was to compare the pregnancy rates between the two groups. The secondary objectives included comparing fertilization rates, oocyte grades, and cleavage rates. Results The pregnancy rates and cleavage rates measured on Day 2 and Day 3 of fertilization were similar in both groups. The fertilization rate (median(IQR)) was higher in the Iso group, but the difference was not statistically significant (air - 100 (87.5-100) vs. N₂O - 100 (83.3-100); P = 0.07). The number of oocytes retrieved of Grade 1 and Grade 2 quality was similar in both groups, while Grade 3 oocytes retrieved were significantly higher in the N₂0 group. Conclusion While the use of N₂O during oocyte retrieval appears to be associated with an increased number of lower-quality oocytes, it does not negatively affect fertilization, cleavage, or pregnancy rates.