P-031 The extent of late paternal effect: does the blastocyst matter? A retrospective analysis of 703 single, frozen-thawed embryo-transfers
Authors: Dolci C , Vanni V.S , Papaleo E , Pagliardini L , Cermisoni G , Salmeri N , Salonia A , Candiani M 
Published: June 2022

Abstract

Study question
Do the blastocysts derived from severe male infertility show different ongoing pregnancy rates(OPR) compared to blastocysts of couples requiring assisted reproduction techniques(ART) for other indications?

Summary answer
First, single, frozen-thawed embryo transfers of blastocysts derived from severe male infertility did not affect OPR in-vitro fertilization (IVF)/ intracytoplasmic sperm injection (ICSI) cycles.

What is known already
Several studies reported a negative impact of severe male infertility on fertilization rate, embryo morphology and embryo cleavage speed, due to the so-called early paternal effect, caused by sperm cytoplasm deficiencies. Nuclear sperm defects are responsible for the late paternal effect, causing lower blastocyst formation rates and, theoretically, reducing implantation potential of the obtained blastocysts. However, the effects of male infertility on OPR and live birth rates (LBR) are still debated. Additionally, the heterogeneity in the definition and estimation of male infertility makes the existing data difficult to interpret.

Study design, size, duration
Retrospective analysis of first IVF/ICSI cycles performed between January 2019 and December 2021 in the Reproductive Sciences Unit of Gynaecology/Obstetrics Department of San Raffaele Hospital in Milan, Italy.

Participants/materials, setting, methods
First, single, frozen-thawed embryo transfers of infertile couples first IVF/ICSI cycles were included. Embryo transfers obtained by frozen semen were excluded. Couples characteristics, semen parameters and controlled ovarian stimulation (COS) data were collected. Semen quality was assessed using total motile count (TMC) and grouped into quartiles of TMC for the analyses. The effect of severe male factor infertility evaluated through TMC over OPR was the primary outcome of the study.

Main results and the role of chance
N = 703 transfers were analysed. Performing a logistic regression analysis adjusted for confounding factors (maternal age, COS protocols, number of oocytes retrieved and quality of transferred blastocysts), OPR was not influenced by TMC values [odds ratio (OR) = 0.999; confidence interval (CI) = 0.986-1.013; p = 0.932]. After grouping male infertility population into quartiles of TMC, no significant differences in OPR were found between extreme quartiles (TMC ≤2.55 million and TMC ≥20 million respectively), even when adjusted for confounders [OR = 1.007; CI 0.609-1.663; p = 0.98]. Therefore, the implantation potential of the obtained blastocysts, once formed, seems to be independent from sperm quality.

Limitations, reasons for caution
The major limitations of the present study are the retrospective design and sample size. Additionally, the estimation of male infertility as well as the routinary use of TMC in clinical practice are not yet standardized. However, having analysed only the first transfers of the included couples makes our results reliable.

Wider implications of the findings
Further prospective studies with larger sample size are needed to confirm our results and to validate the use TMC as a standard tool to classify male factor and to guide clinical choices. Pregnancy and obstetrical outcomes are also necessary to better understand the role of male infertility in human reproduction.

Trial registration number
not applicable