Using blastocyst re-expansion rate for deciding when to warm a new blastocyst for single vitrified-warmed blastocyst transfer.

Research Question: Can predictive post-warm parameters that support the decision to transfer a warmed blastocyst or to warm another blastocyst be identified in women with multiple frozen-vitrified blastocysts?

Design: Retrospective single-centre observational cohort analysis. A total of 1092 single vitrified-warmed blastocyst transfers (SVBT) with known Gardner score, maternal age and live birth were used to develop live birth prediction models based on logistic regression, including post-warm re-expansion parameters. Time-lapse incubation was used for pre-vitrification and post-warm embryo culture.

Endometrial preparation methods prior to frozen embryo transfer: A retrospective cohort study comparing true natural cycle, modified natural cycle and artificial cycle.

Purpose: The aim of this study was to compare the outcomes of three endometrial preparation methods prior to frozen embryo transfer (FET): Natural cycle (NC), modified natural cycle (mNC), and programmed/artificial cycle (AC) protocols. Primary outcomes investigated were clinical pregnancy rate (CPR) and live birth rate (LBR).

Methods: A retrospective study on 2080 FET cycles including patients ≤ 35 years with a BMI ≤ 30 who underwent FET with a single autologous blastocyst stage embryo at Aarhus University Hospital or Horsens Regional Hospital in the period 2013-2019.