O-293 Mastering consistency: a similar training allows to standardize embryo transfer performance, but experience does not involve further improvements
Authors: Ruffa A , Cimadomo D , Innocenti F , Taggi M , Pittana E , Colamaria S , Argento C , Giuliani M , Petrone P , Rucci C , Maggiulli R , Rienzi L , Ubaldi F  M , Vaiarelli A 
Published: July 2024

Study question

Is there any variation in the live birth rate (LBR) per vitrified-warmed single euploid blastocyst transfer (SEBT) among clinicians trained at the same IVF center?

Summary answer

The LBR per SEBT (overall: 53%) remained consistent among equally trained transfer operators (range: 48%-60%) regardless of the number of prior procedures performed.

What is known already

The number of ART treatments and practitioners has increased over the years. To ensure high standards, an efficient quality control system should monitor and standardize operators’ performance by leveraging statistically-sound key-performance-indicators (KPIs). The embryo transfer procedure is a clinically relevant step, particularly susceptible to variations among clinicians, irrespective of their experience. However, the outcome of “LBR per transfer” is influenced by various confounders, such as embryo stage, morphology, reproductive history, uterine conditions, and others. Our objective was to assess potential differences among transfer practitioners who underwent the same training at a single IVF center in the least biased scenario possible.

Study design, size, duration

Retrospective single center study. Out of 8663 transfers performed by 4 operators (all trained by operator-1) between 2013 and 2021, we selected 421 first vitrified-warmed transfers with day5 euploid blastocysts whose morphology was &gt;Gardner’s BB-grade in non-obese women, thereby excluding all main confounders on our primary outcome (= LBR per SEBT across different operators). The study was powered to exclude a 18%-decrease (β = 0.8, α = 0.05) in the LBR versus operator-1 (ratio comparator:control=1:2).

Participants/materials, setting, methods

We conducted ICSI, blastocyst biopsy without day3 zona-drilling, and aneuploidy testing to exclude full-chromosome uniform aneuploidies. All blastocysts were transferred ∼2 hours after warming. Uterine assessment was conducted to exclude putative conditions associated with lower LBR. Endometrial preparation protocol (modified-natural cycle versus hormone-replacement-therapy), maternal age at transfer, experience of prior implantation(s) (yes/no), the embryologists involved in the transfer procedure, were assessed as putative further confounders. All significant differences were confirmed through regression analyses.

Main results and the role of chance

The overall LBR per vitrified-warmed SEBT was 53.4% (N = 225/421). Operator-1 conducted 3960 transfer procedures during the study period, with 167 eligible for this study, achieving a 55.7% LBR (N = 93/167). Operator-2,-3, and -4 respectively conducted 2533, 1087, and 1083 procedures during the study period, with 134, 62, and 58 eligible for this study. Their LBRs were 50% (N = 67/134, p-value versus operator-1=0.2), 48.4% (N = 30/62, p-value=0.2), and 60.3% (N = 35/58, p-value=0.3). Multivariate logistic regression analysis, adjusted for endometrial preparation protocol and embryologists involved in the transfer procedure, confirmed the absence of an association (Operator-2 vs. 1 multivariate-OR: 0.83, 95%CI 0.5-1.39, adjusted-p=0.49; Operator-3 vs. 1 multivariate-OR: 0.75, 95%CI 0.40-1.40, adjusted-p=0.37; Operator-4 vs. 1 multivariate-OR: 1.40, 95%CI 0.72-2.70, adjusted-p=0.32). Importantly, the number of prior transfer procedures conducted by each clinician during the study period also showed no association with the primary outcome (OR = 1.0, p-value=0.82). From an IVF center perspective, the LBR per SEBT remained stable across the 9-year study period, showing minimal non-significant fluctuations. These outcomes describe an IVF center where equally-trained clinicians adopt the same standard-operating-procedures to manage vitrified-warmed embryo transfers. In this context, the LBR per SEBT represents an ideal KPI to assess the learning curve of operators in training.

Limitations, reasons for caution

Over 2500 SEBTs are required to rule out a 5%-decrease in the LBR. Yet, such a substantial number is better suited for comparing centers’ rather than practitioners’ performance. It would be intriguing to investigate potential differences among operators who underwent different training regimens but operate within the same clinic.

Wider implications of the findings

No correlation exists between the number of prior embryo transfer procedures conducted and further improvements, therefore initial operators’ training is crucial for standardizing their performance. LBR per SEBT is a strong KPI, though poorly-actionable in the short-term. It’s better suited for center comparisons, prompting internal procedure reviews when differences arise.

Trial registration number

not applicable