Advanced Paternal Age Reduces Live Birth Rates in Normospermic Men Undergoing ART: A Large Retrospective Cohort Study

The impact of maternal age on assisted reproductive technology (ART) outcomes is well established, whereas the contribution of paternal age remains less clearly defined, particularly among men with normal semen parameters.

To evaluate the association between paternal age and live birth outcomes in couples undergoing in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) when the male partner is normospermic.

We conducted a retrospective cohort study based on a prospectively maintained clinical database including 6262 couples undergoing their first fresh embryo transfer between 2018 and 2024 at a tertiary reproductive medicine centre. Normospermia was defined according to World Health Organization (WHO) 2021 criteria. The association between paternal age and live birth was assessed using multivariable logistic regression models adjusted for maternal age. Sensitivity analyses included additional adjustment for anti-Müllerian hormone (AMH) and Poisson regression with robust standard errors. Missing data were handled using multiple imputation.

Among the 6262 couples, 2678 (42.8%) involved normospermic men. In multivariable logistic regression analyses, advancing paternal age was significantly associated with lower odds of live birth (OR: 0.943 per year; 95% CI, 0.932-0.955; p < 0.001). The association remained consistent after multiple imputation (OR: 0.941; 95% CI, 0.931-0.952; p < 0.001) and in sensitivity analyses including AMH (OR: 0.969; 95% CI, 0.950-0.987; p = 0.003). No significant interaction was observed between paternal age and fertilisation technique (IVF vs. ICSI).

Advancing paternal age is associated with a reduced probability of live birth in ART, even among normospermic men and after accounting for maternal age. This effect, although modest on a yearly basis, may translate into a clinically meaningful cumulative decline in reproductive success over time. These findings highlight paternal age as a clinically relevant factor in reproductive counselling and prognostic assessment.