Paternal ageing impacts blastulation and the outcomes of pregnancy at different levels of maternal age: A clustering analysis of 21,960 oocytes and 3837 ICSI cycles.

The objective of this cross-sectional study was to investigate the impact of paternal age on the outcomes of intracytoplasmic sperm injection (ICSI) cycles at different values of maternal age. A total of 21,960 injected oocytes deriving from 3837 ICSI cycles performed between January 2014 and October 2020, performed in a private university-affiliated in vitro fertilization centre was included. The main effects of maternal and paternal age, as well as the effect of their product (interaction term) on embryo development and pregnancy outcomes were investigated considering the clustering of data. The coefficients for the interaction term were statistically significant for blastocyst development, top-quality blastocyst, implantation, pregnancy, miscarriage, and live-birth rates. For every 1-year increase in paternal age, the odds ratio of live-birth reduces by 1% in females aged 37 years, 1.6% in those aged 38 years, 2.4% in 39-year-old females, 5% in 42-year-old females and so on. An increase in the interaction term by 1 year decreases the pregnancy rate by 0.4% and live-birth rate by 0.8 and increases the miscarriage rate by 1.2%. The slopes of maternal age on blastulation, blastocyst quality, and implantation, pregnancy, miscarriage, and live-birth rate significantly changed (worsened) for every year increase in paternal age.