P-778 High altitude significantly affects pregnancy, implantation, live birth, and miscarriage rates in patients subjected to in vitro fertilization procedures with donated oocytes

Abstract Study question Is high altitude an important factor that affects the clinical outcomes in patients subjected toin vitrofertilization with donated oocytes? Summary answer Pregnancy, implantation, and live birth rates are significantly impacted by paternal chronic hypoxia in IVF procedures involving egg donors. What is known already High altitude is characterized by low temperatures, high UV radiation, and a hypoxic environment that significantly affect human physiology, including endocrine, cardiovascular, metabolic, and reproductive functions. Hypoxia can affect male reproduction differently, such as at the hormonal level, during spermatogenesis and gene expression. More importantly, hypoxia can affect key events during early embryo development, with time of exposure being the determining factor in the stage of fertilization and embryonic development in mammals. Study design, size, duration The following work is a retrospective nonrandomized study based on data from 85 IVF donor egg cycles performed at high altitude (Huancayo-Peru, 3,300 meter above sea level;n = 42) and at sea level (Guayaquil-Ecuador;n = 43) between July 2019 and December 2020. The same protocols of culture and embryo classification were used in both assisted reproduction laboratories. Participants/materials, setting, methods Anonymous oocytes donors (18-29 years old) underwent physical, gynecological and psychological examinations, with no family histories of hereditary or chromosomal diseases reported. According to seminal samples, IVF or ICSI was elected as the insemination procedure. Extended embryo culture until blastocyst stage was done in all procedures. Pregnancy, implantation, live birth, and miscarriage rates were compared between groups. Main results and the role of chance Out of a total of 983 included oocytes, 529 corresponded to high level patients; and 454, to sea level patients. Fertilization rates (95.1% vs 92.1%) and good-quality embryos at day 3 (79.7% vs 83.8%) were similar between high altitude and sea level groups (P > 0.05). The number of transferred embryos in recipients at high altitude was significantly higher compared to those transferred in recipients at sea level (1.90±0.29 vs 1.62±0.49) (P < 0.05). Blastocyst formation rates (39.3% vs 44.3%), pregnancy rates (61.9% vs 71.4%), implantation rates (48.8% vs 64.7%) and live birth rates per embryo transfer (46.3% vs 65.7%) were significantly lower in the patients at high altitude compared to those from sea level (P < 0.05). Significantly more miscarriages were observed at high altitude (23.1% vs 6.5%) (P < 0.05). Seminal parameters were similar between both evaluated groups. Limitations, reasons for caution The retrospective nature of this study and the small sample size may be reason for caution. Wider implications of the findings The negative effect of high altitude on reproduction has been shown previously in men, hypoxia could cause a degeneration in the germinal epithelium that affects spermatogenesis. We show that paternal chronic hypoxia affects preimplantation embryonic development, pregnancy, implantation, live birth, and miscarriage rates in IVF procedures using donated oocytes. Trial registration number not applicable