Does Fresh Single Embryo Transfer Outcome Predict the Result of a Subsequent Vitrified-Warmed Single Blastocyst Transfer of the Same Cohort?

Objective: to assess whether the outcomes of a fresh single blastocyst transfer may predict the result of a subsequent vitrified-warmed single blastocyst transfer, using embryos from the same cohort.

Design: A retrospective cohort study.

Materials and methods: All vitrified-warmed single blastocyst transfers conducted between 2012 and 2014 were reviewed. Data about the fresh cycle in which the embryos were created, as well as data about the following vitrified-warmed cycle, were collected. Post ‘freeze all’ cycles were excluded.

Results: A total of 1127 cycles were included; Vitrified-thawed cycles following a fresh cycle that ended in a live birth, were significantly more likely to result in a clinical pregnancy, as compared to those following a fresh cycle which failed to reach a live birth (40.5% VS. 32.8%, P value 0.035). Live birth rate at the frozen thawed cycel demonstrated the same trend: 25.6% post live birth in the fresh cycle vs. 19.9% post non-birth, P value 0.06. In a sub-analysis, the chance for a live birth in the vitrified-thawed cycle was tested according to the following outcomes of the previous same-cohort fresh cycle: not pregnant, chemical pregnancy, extra uterine pregnancy,1^st trimester miscarriage, 2^nd trimester miscarriage/stillbirth and live birth. The proportions differed as following, though have not reached a statistical significance: 20.7%, 19.5%, 17.7%, 20%, 12% and 25.6% respectively.

Conclusion: Live birth achieved in a fresh cycle is a favorable prognostic factor for a clinical pregnancy and possibly for a live birth in vitrified-warmed single blastocyst transfer from the same cohort of embryos.