Single embryo transfer of vitrified warmed blastocysts yields equivalent live birth rates and improved neonatal outcomes compared with fresh transfers

After 1,157 fresh and 645 vitrified-warmed day-5 single-blastocyst transfers, we found vitrified warmed blastocysts yielded equivalent birth rates and improved neonatal outcomes compared with fresh transfers.

Tammie K. Roy, Ph.D., Cara K. Bradley, Ph.D., Mark C. Bowman, M.B.B.S., Ph.D., FRANZCOG, CREI, Steven J. McArthur, B.Sc.

Volume 101, Issue 5, Pages 1294–1301.e2


To compare pregnancy and neonatal outcomes after fresh and vitrified-warmed single-blastocyst transfers.

Retrospective study.

Private in vitro fertilization (IVF) clinic.

1,209 infertile patients who underwent a total of 1,157 fresh and 645 vitrified-warmed embryo transfers.

Day-5 single-blastocyst transfers using fresh or vitrified-warmed (Cryotop method) grade I and grade II embryos.

Main Outcome Measure(s):
Fetal heart pregnancy rate, live-birth rate, gestational age, and live-birth weight.

The overall blastocyst thaw survival rate was 94.4% and was not significantly different between blastocyst grades or developmental stages. Similar clinical outcomes were achieved for fresh and vitrified-warmed blastocyst transfers; for example, grade I blastocysts had a live-birth rate of 52.8% versus 55.3%, respectively, and grade II blastocysts had a rate of 34.9% versus 30.4%, respectively. Significantly improved neonatal outcomes were evident for vitrified-warmed blastocyst transfers for gestational age, being on average 0.3 weeks longer, and for live-birth weight with babies born on average 145 g heavier (3,296 g versus 3,441 g for fresh and vitrified-warmed groups, respectively), as compared with fresh transfers.

Embryo transfer of vitrified-warmed blastocysts yields equivalent live-birth rates and improved neonatal outcomes compared with fresh transfers.

  • Lauren Johnson

    I congratulate the authors on publication of their manuscript. The question of whether fresh or frozen transfer yields better pregnancy rates and neonatal outcomes is timely. I was hoping that the authors would address a question about the manuscript. I noticed that women in the vitrification group were significantly younger and more likely to have tubal factor infertility compared to other infertility diagnoses. Both of these factors are associated with better prognosis, which could confound the results. Were the authors able to control for potential confounders when performing the analysis?

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