Analysis of clinical outcomes of vitrified-warmed embryo transfer after IVF/ICSI at high altitude (3650 m) in Tibet.

Research Question: What are the pregnancy outcomes of IVF vitrified-warmed embryo transfer (IVF-FET) carried out in a clinical setting located at an altitude of 3650 m in Tibet, China?

Design: A retrospective analysis of 238 infertility couples (n = 344 treatment cycles) who underwent FET treatment at the Xizang Fukang Hospital, Tibet. The overall clinical pregnancy rate, implantation rate, live birth rate, miscarriage rate and ectopic pregnancy rate were statistically analysed. Women were categorized into two groups based on age: 35 years or younger (n = 265 cycles) and over 35 years (n = 79 cycles). The general characteristics and pregnancy outcomes were compared between the two groups.

Results: The clinical pregnancy rate, implantation rate, live birth rate, miscarriage rate, and ectopic pregnancy rate of the 344 FET cycles were 43.02%, 30.90%, 35.17%, 18.24% and 1.35%, respectively. The clinical pregnancy rate (46.04% versus 32.91%), implantation rate (33.92% versus 21.01%) and live birth rate (38.11% versus 25.32%) in the group aged 35 years or younger were significantly greater than those in the group aged over 35 years (P = 0.039, P = 0.004, P = 0.037). The miscarriage rate (17.21% versus 23.08%) and ectopic pregnancy rate (0.82% versus 3.85%) were not significantly different in the two groups.

Conclusion: A live birth rate of 35.17% can be achieved with IVF-FET in high-altitude areas (3650 m above sea level). Maternal age is still an important determinant of clinical pregnancy rate, implantation rate, and live birth rate of infertile patients in high-altitude areas.