P-112 Outcome of laser collapsing blastocyst on clinical pregnancy rate
Authors: Urkimbayeva D 
Published: June 2023

Abstract

Study question
To determine clinical pregnancy rate after laser-induced collapse of blastocyst before cryopreservation

Summary answer
Laser collapse of the blastocyst before cryopreservation increases clinical pregnancy rate regardless of assigned embryo quality group compared to the blastocysts vitrified without laser collapsing

What is known already
Vitrification has been associated with the certain risks to the structure of an embryo due to intracellular ice crystal formation and impaired shrinkage rate. Blastocyst is a large fluid filled cavity requiring additional preparation to reduce the potential risks of damage. Collapsing a blastocyst has been shown to improve survival rate of an embryo following thawing and improve in vitro fertilization (IVF) outcomes including clinical pregnancy and live birth rates

Study design, size, duration
. It is a single-centre retrospective study conducted at a private clinic in Kazakhstan. We analyzed the outcome of IVF treatment following cryopreservation and subsequent frozen embryo transfer of 2959 blastocysts from 1642 women during January 2019-December 2021

Participants/materials, setting, methods
The data on blastocyst cryopreservation technique and IVF treatment outcome was collected from the clinic’s electronic database. The blastocysts were divided into two groups based on performed laser collapsing prior to vitrification and further stratified by embryo quality group including excellent, good and fair groups. The primary outcome was clinical pregnancy rate. Laser-assisted collapsing procedure was initiated in August 2020 at the clinic. Thus, all previously vitrified blastocysts served as control group for the study

Main results and the role of chance
1556 blastocysts from 777 women vitrified following laser collapsing and 1403 blastocysts from 865 women without prior laser collapsing were analyzed in the study. Stratification of blastocysts by the embryo quality were comparable between two groups with more than half of embryos defined as excellent embryo quality group, 54% in collapsed group and 52% in non-collapsed group (p &gt; 0.05). Most blastocysts were from women under the age of 35 years old in both study groups. 1 in 4 collapsed blastocysts of the excellent embryo quality group were from women older than 35 years old, whereas non-collapsed group of blastocysts was evenly distributed between embryo quality groups (p &lt; 0.05). Clinical pregnancy rate was the highest in the excellent embryo quality group with prior laser collapsing compared to the group without collapsing, 53% vs 43% respectively (p &lt; 0.001). Overall, collapsed blastocysts showed higher rate of clinical pregnancy rate in all three embryo quality groups. Despite of changes associated with the COVID-19 pandemic IVF outcomes had not been affected but improved with the use of laser collapsing prior to embryo vitrification

Limitations, reasons for caution
Retrospective design of the study did not provide full baseline information on potential confounders including paternal characteristics and concurrent conditions. Moreover, the study period included the COVID-19 pandemic start which could have affected treatment outcomes

Wider implications of the findings
Collapsing the blastocyst embryo before vitrification should become a routine procedure to improve treatment outcomes of frozen embryo transfer irrespective of woman’s age and embryo’s quality

Trial registration number
not applicable