P-528 Time-lapse monitoring: an adjunct tool to select embryos for preimplantation genetic testing
Authors: Setti A , Braga D , Guilherme P , Iaconelli A. , Borges Junior E 
Published: June 2022

Abstract

Study question
Does embryo aneuploidy have any impact on embryo morphokinetic events in a time-lapse imaging (TLI) culture system?

Summary answer
Aneuploidy had a significant impact on early and late embryo morphokinetic events. Mosaic and aneuploid embryos behaved similarly in terms of morphokinetics.

What is known already
The preimplantation genetic testing (PGT) emerged as an approach to analyse embryos’ DNA for determining genetic abnormalities, distinguishing chromosomally normal embryos, considered to have high developmental potential, from their aneuploid siblings. Although shown to be efficient and clinically relevant, the invasive nature of the technique limits its success. Given the challenges associated with invasive embryo biopsy, ongoing studies are now seeking for non-invasive assessments of the embryo DNA. Timelapse imaging (TLI) may allow the identification of morphokinetics events affected by aneuploidy, which could be a powerful tool for improving embryo selection for transfer, without the detrimental effects of embryo biopsy.

Study design, size, duration
This case-control study was performed in a private university–affiliated IVF center, between 2019 March and 2020 December. Kinetic data were analyzed in 957 embryos, derived from 316 patients undergoing ICSI cycle with PGT-A. Kinetic markers from the point of insemination were recorded. Generalized linear models followed by Bonferroni post hoc were used to compare timing of specific events in euploid (n = 352), aneuploid (n = 583) and mosaic embryos (n = 22). The post hoc achieved power was &gt; 80%.

Participants/materials, setting, methods
Embryos were cultured in the EmbryoScope incubator, which recorded the following kinetic markers: timing to pronuclei appearance and fading (tPNa and tPNf), two (t2), three (t3), four (t4), five (t5), six (t6), seven (t7), and eight cells (t8), morulae (tM), start of blastulation (tSB) and blastulation (tB). Durations of second and third cell cycles (cc2 and cc3) and timing to complete synchronous divisions s1, s2, and s3 were calculated. The KIDScore ranking was recorded.

Main results and the role of chance
Aneuploid embryos showed significantly longer tPNf, t2, t3, t4, t6, t7, t8, tM, tSB, tB, s2 and s3 compared to euploid embryos. The KIDScore day 5 also rank was significantly lower in aneuploid embryos compared to euploid ones. As for mosaic embryos no significant differences were observed in the comparisons of means of morphokinetic events and KIDScore rank, but regression analyses showed an increased chance of mosaicism among embryos with longer tPNf, t2, t3, t6, t7, tM, tB, as well as a inverse association with KIDScore rank, when compared with euploid embryos. Embryos were hierarchically distributed into quartiles according to the KIDScore rank: Q1 ≤3.9, Q2 4-5.6, Q3 5.7-7.5, and Q4 ≥7.6. Euploidy incidence was significantly different among the KIDScore quartiles, in which the percentage of euploidy increased directly proportional to the kidscore rank. For patients &gt;35 years old, the logistic regression analysis demonstrated that comparing with embryos in the Q4, embryos in the Q1, Q2, and Q3 have a decreased chance of being euploid. For patients ≤35 years old, comparing with embryos in the Q4, embryos with KIDScore D5 in the Q1 and Q2, but not in Q3, have a decreased chance of being euploid.

Limitations, reasons for caution
Our study is limited by its retrospective nature and small casuistic, despite adequate power has been achieved. The reason for the lack of consistency with some previous findings can be explained by variations in culture systems, studied population, embryo stage for biopsy and wide range of tests used for PGT.

Wider implications of the findings
Our evidence suggests that TLI monitoring may be an adjunct approach to select embryos for PGT, however, cautious investigation is still needed. The mechanism by which embryo aneuploidy may alter the cleavage timing of embryos is undefined, but disruptions of mitosis, cell-cell interactions and blastocyst differentiation are possible candidates.

Trial registration number
not applicable