P–266 Morphometric assessment of Ratio of inner-cell-mass diameter to blastocyst diameter is an effective criterion to select best embryo for successful outcomes in single blastocyst transfer-cycles
Authors: Chimote N M , Chimote B 
Published: August 2021

Study question

Can semi-quantitative measurement of ICM diameter vis-à-vis blastocyst diameter, calculated from photographic images, be a significant predictor of implantation potential in single blastocyst transfer cycles?

Summary answer

A simple, non-invasive measurement of ICM:Blastocyst diameter ratio is a potentially effective predictor of high developmental potential, implantation, live-birth rates in single blastocyst transfer cycles. What is known already: Correlationship between quantitative measurements of blastocyst morphology such as size and shape of ICM and its implantation potential were first reported by Richter et al. Widely used Gardner and Schoolcraft’s qualitative scoring assessment is based on three major variables: expansion stage of blastocyst, cohesiveness of the inner cell mass (ICM), and consistency of trophectodermal (TE) cells. A top quality single blastocyst transfer yields implantation rate nearing 70% and live-birth rate about 50%. If an additional morphological but vital parameter evaluating ICM:Blastocyst diameter ratio is introduced to the Gardner’s blastocyst gradation system, it may help enhance IVF success rates still further.

Study design, size, duration

A prospective observational cohort study of women (n = 244) undergoing IVF treatment at our private fertility clinic from April 2018 until March 2020.

Women with their autologous fertilized oocytes undergoing extended culture and transfer of a single fresh, at least fully expanded (Grade 3) blastocyst with a measurable ICM diameter and blastocyst inner diameter on day 5/6, irrespective of age, cycle number and indication for treatment, were included. Cryopreservation cycles were excluded.

Participants/materials, setting, methods

Each blastocyst was evaluated for expansion grade, ICM and TE according to Gardner et al. conventional method. Additionally, ratio of ICM diameter w.r.t. blastocyst inner diameter was also calculated from the photographic images on screen using the Hamilton-Thorne software package embedded with their laser system. Measurements were done on blastocysts where expansion had occurred between 114 and 120 hours after insemination. Implantation rates and live-birth rates were the major end-points.

Main results and the role of chance

A total of 244 blastocyst transfers were performed in same number of women, and 130 clinical pregnancies were achieved (53.3%). The average age of the women was 32.5 ± 4.2 years. The blastocysts that implanted successfully had an average ICM:blastocyst diameter ratio of 0. 469±0.082), whereas blastocysts that did not implant had a significantly lower ratio of 0.325±0.09 (P &lt;.0001). No statistical significant difference was found in the TE grade between the blastocysts that implanted successfully and those that did not. Out of the 130 pregnancies achieved, 89 (68%) resulted in the delivery of a healthy baby. After ROC analysis, a cutoff value for the ICM/blastocyst ratio showed equal rank for sensitivity (0.81) and specificity (0.72). The resultant positive predictive value was 78%, and the negative predictive value was 74%. In our study, the conditional probability of achieving pregnancy upon transfer of a single blastocyst with an ICM:blastocyst ratio higher than the cutoff value of 0.4255 was 76%. This was significantly higher than the probability of pregnancy from blastocysts graded by conventional morphometry.

Limitations, reasons for caution

Our study is limited by the small sample size. Hence more multicentric studies are warranted to observe similar conclusion. Wider implications of the findings: The strengths of the study are the performance of single blastocyst transfers and using live births as the measurement endpoint. It is important to mention that embryo grading is inevitably subject to intra- and interobserver variations. However, with simple measurements of image data recording eliminates a degree of these variations.

Trial registration number

Not applicable