HealthDay News — Prolonged storage of embryos after vitrification is associated with a reduced likelihood of biochemical pregnancy, clinical pregnancy, and live birth, according to a study published online June 23 in Human Reproduction.
Jianghui Li, from the JiaoTong University School of Medicine in Shanghai, and colleagues performed a retrospective study among 24,698 patients with the first vitrified embryo transfer following a freeze-all strategy during January 2011 to December 2017. Data were included for 24,698 patients who were classified according to storage time: 11,330 in Group 1 (storage time less than three months); 9,614 in Group 2 (three to six months); 3,188 in Group 3 (six to 12 months); and 566 in Group 4 (12 to 24 months).
The researchers found that compared with Group 1, with increasing storage time, there was a significant decrease in the likelihood of biochemical pregnancy (adjusted odds ratios, 0.92, 0.83, and 0.68 for Groups 2, 3, and 4, respectively), clinical pregnancy (adjusted odds ratios, 0.91, 0.80, and 0.65 in Groups 2, 3, and 4, respectively), and live birth (adjusted odds ratios, 0.89, 0.83, and 0.59 in Groups 2, 3, and 4, respectively) after adjustment for potential confounding factors. The associations of miscarriage and ectopic pregnancy to storage time did not reach statistical significance.
“Our results suggest that clinicians should consider the effect of storage duration before making decisions about the numbers of embryos to freeze and store,” a coauthor said in a statement.