Is paternal age associated with timing, stage, morphology, and implantation of the competent blastocyst: a multicenter cohort study

Is age of men undergoing assisted reproductive technology associated with timing, stage, morphology, and implantation of the competent blastocyst?Advanced paternal age was associated with reduced development speed and level of hCG in the competent blastocysts in COS treatments.We have shown that for every one-year increase in women’s age there is a 5\ we have shown that the initial hCG rise is associated with women’s age with the youngest women having the lowest hCG level. It is unknown whether the age of men undergoing ART treatment is associated with the timing (day 5 or 6), the development stage, morphology, and the early implantation of the competent blastocyst.This is a multicenter historical cohort study based on data from 16 private and university-based public fertility clinics where 7246 men and women, between 2014 and 2018, underwent controlled ovarian stimulation (COS) or Frozen-thawed Embryo Transfer (FET) with a single blastocyst transfer resulting in a singleton pregnancy. These data were linked to the Danish Medical Birth Registry, resulting in inclusion of 4842 men with a partner giving birth.Exposure (age) and outcome data (blastocyst timing (day 5 or 6), development stage (3-6), inner cell mass (ICM)(A,B,C), trophectoderm (TE)(A,B,C) and hCG were collected from the database, Danish Medical Data Center. All COS cycles (IVF and ICSI) and FET cycles (natural and substituted), were included. Exclusion criteria were cycles with pre-implantation genetic testing, donated oocytes and semen. The analyses were adjusted for female age, female smoking, female BMI, diagnosis and clinic.The adjusted association between paternal age and transfer day in COS treatments showed that for every increase of one year, men had a 6\ compared to day 5 (OR 1.06, 95\1.00;1.13). The mean difference in hCG values when comparing paternal age group 30-34, 35-39 and 40-45 with the age group 25-29 in those receiving COS treatment, all showed significantly lower adjusted values for older men. In FET treatments, none of the investigated associations reached statistical significance.The blastocyst morphology was subjectively assessed, and information bias may have influenced the results. However, adjusting for clinic takes the potential influence of variation in embryo scoring between clinics into consideration.We hypothesize that the later transfer (day 6) in female partners of older men is likely to be due to longer time spent by the oocyte to repair fragmented DNA of the sperm cells, which should be a focus of future research in men.“not applicable”