P-149 The 1st polar body morphology in doubling oocytes technique: does it matter?
Authors: Ilyin I , Gontar J , Buderatskaya N , Lavrynenko S , Kazachkova N , Parnitskaya O , Herevich Y , Kapustin E , Lakhno Y 
Published: June 2022

Abstract

Study question
Does any morphology type of the 1st polar body (PB) useful for transfer in oocytes and embryo doubling?

Summary answer
The 1stPB morphology plays a key role in the transfer technique efficiency

What is known already
Well known that chromosomal set of the 1stPB is corresponding to chromosomes remaining in the oocyte. This fact is the basis of the transfer technique that helps patients with low ovarian reserve and poor response to increase the chances of having a biologically native child. As practice shows, the shape and size of the 1stPB can vary even among oocytes obtained by the same aspiration of the same patient. Therefore, it is very important to know which morphological type of the 1stPB should be used when applying the transfer technique in order to obtain the best results.

Study design, size, duration
The study was performed in the Medical Center IGR from December 2017 to December 2021 and involved 75 from 93 patients (mean age 39.2±5.1 years), because 288 of their 1stPBs had indicated morphology of the following types: local fragmentation(LF,n=79), ovoid rough(OR,n=70), round smooth(RS,n=56), irregular shape(IS,n=41), small(S,n=17), flat(F,n=11), round rough(RR,n=7), large(L,n=4), ovoid smoth(OS,n=3).We evaluated the pronuclear scoring, number of embryos on the 3rd and the 5th post-fertilization day, euploidy according to morphological types of the 1stPB

Participants/materials, setting, methods
We used patients’ oocytes and their 1stPBs obtained from 75 women with low ovarian reserve and poor response. Donor oocytes have been previously enucleated and modified by the transfer of patients’ 1stPB with further fertilization. The procedure was carried out using Nikon Ti Eclipse(Japan) inverted microscope, Saturn 3 laser console(UK). Preimplantation genetic testing for aneuploidy was performed using trophectoderm biopsy. Samples were diagnosed using Ion S5(USA). Statistical analysis was carried out using Chi-square test.

Main results and the role of chance
To evaluate the effectiveness of the transfer technique, the 1stPBs morphological types suitable in quantity for statistical processing, were compared. The number of 2PN pattern during pronuclear scoring was distributed among morphological types (LF:OR:RS:IS:S) with the following percentages 58.2:71.4:75.0:63.4:63.7, respectively. Statistically significant difference (SSD) was found only between RS and LF types(p &lt; 0.05). Among the developing embryos on the 3rdday the largest number was obtained using the 1stPBs of the RS morphological type with SSD relative to the type LF(78.6% vs.50.6%,p&lt;0.005), OR(78.6% vs.40.0%,p&lt;0.005), IS(78,6% vs.53.7%,p&lt;0.01). On the 5thday the number of developing embryos was unevenly distributed namely LF:OR:RS:IS:S as a percentage 11.4:31.4:37.5:24.4:11.8, respectively. It is worth noting that SSD was found between LF and RS types (p &lt; 0.005) and LF and OR types(p &lt; 0.005). With regard to the number of high quality blastocysts(HQB), the use of type S didn’t lead to the formation of HQB and the worst result among morphological types with the presence of HQB was shown by the LF type with confirmed SSD (p &lt; 0.005). The percentage distribution was as follows: LF:OR:RS:IS corresponded to 6.3:22.9:25.0:9.8. Percentage of euploid embryos relative to the number of examined blastocysts by types LF:OR:RS:IS was 28.6:35.3:29.4:14.3, respectively, SSD wasn’t found between the morphological types(p &gt; 0.05).

Limitations, reasons for caution
The shape and size of the 1stPBs is assessed visually, so results will vary between laboratories. For standardization, it is necessary to use programs that allow measuring the size and perform photo fixation of the shape.

Wider implications of the findings
Results of study shows that the use of certain morphological types of the 1stPBs has a higher efficiency. It‘s noteworthy that the best results were obtained when using round smooth polar bodies, what is important to understand in predicting the IVF program outcome and the adequate consumption of donor oocytes.

Trial registration number
N/A