P–232 A trophectoderm morphology can predict a live birth rate and gender imbalance
Authors: Mungunshagai B , Sengebaljir D , Ganbaatar C , Tserendorj T , Enkhsaikhan B , Dorjpurev A , Ganbat G , Boris T , Khangarid A , Jamiyansuren J 
Published: August 2021

Abstract

Study question
Which morphology parameter is the most predictable in the live birth rate and can affect the sex ratio?

Summary answer
The trophectoderm grade (TE) can predict the live birth rate and skewed to male gender after single vitrified-warmed blastocyst transfers (SVBT).

What is known already
The Gardner and Schoolcraft grading system of blastocyst evaluation with morphology is the major predictor of the clinical outcome in ART. Inner cell mass (ICM) and trophectoderm (TE) morphology are strongly correlated between clinical pregnancy, live birth, and miscarriage. A greater degree of expansion of the transferred blastocysts showed a higher implantation rate. Therefore, it is essential to clarify which parameter is more predictable in clinical outcome during elective SVBT. However, SVBT has some potential limitations, including adverse effects such as a male-biased imbalance in the sex ratio.

Study design, size, duration
The retrospective analysis used 1138 cycles of SVBT in the Ojinmed IVF center, Mongolia, between May 2015 to January 2019. The morphology grade and blastocyst inner diameter compared with clinical pregnancy rate (CPR), live birth rate (LBR), and miscarriage. The sex ratio was estimated for all patients, excluding those who underwent PGT-A, donor oocytes, and monozygotic twins. Blastocyst quality was evaluated with Gardner and Schoolcraft grading system and measured inner diameter of the blastocyst.

Participants/materials, setting, methods
All patients underwent a clomiphene-based minimal ovarian stimulation protocol or drug-free natural cycle IVF treatment. On day 5 to 6, blastocysts that reached an inner diameter &gt;160μm were immediately vitrified. Blastocyst morphology evaluated by ICM and TE grade. The CPR (with a confirmed gestational sac at 6–7 weeks of pregnancy) and the LBR (live birth at 22 weeks of pregnancy over) were estimated per embryo transfer procedure, followed by miscarriage rate.

Main results and the role of chance
The CPR was 44.69%, 38.97%, and 25.91% for A, B, C grades of ICM, respectively. And the LBR was 39.82%, 34.62%, and 19.1% for A, B, C grades of ICM, respectively. TE was strongly related to CPR (aOR=2.47, 95% CI 1.71–3.58, p &lt; 0.01) and LBR (aOR=1.77, 95% CI 1.06–2.96, p = 0.028) in univariate and multivariable logistic regression analysis (A grade vs C grade). Also, CPR and LBR were increased with blastocyst inner diameter, proportionally. The A and B grade ICM blastocysts showed 2.8 - 2.9 times less miscarriage rate than the C grade of ICM in the univariate logistic regression analysis. The result of multivariable logistic regression analysis showed B grade of ICM had 2.3 times less than C grade of ICM (aOR 2.36, CI 95% 1.20–4.61, p = 0.012) and TE, patient age and blastocyst inner diameter were not significantly associated with miscarriage rate. The gender ratio was 56.8% (204/359) for male. The result of multivariable logistic regression analysis showed that A grade TE had a 2.3 times higher probability of male than C grade (aOR 2.31, CI 95% 1.22–4.37, p = 0.01). Neither fertilization method, ICM, expiation grade, nor fertility case was significantly associated with the sex ratio.

Limitations, reasons for caution
The result of the current retrospective study is limited to data from a single IVF center.
Wider implications of the findings: Our study suggests that TE grade is the most predictable and ICM grade was associated with miscarriage. The high grade such as A-grade TE blastocyst transfer has more live birth rate, whereas it can affects at sex ratio in favor of male embryos after SVBT.

Trial registration number
Not applicable