Male ageing is negatively associated with the chance of live birth in IVF/ICSI cycles for idiopathic infertility

STUDY QUESTION: Is male age associated with the clinical outcomes of IVF/ICSI cycles for idiopathic infertility after adjustment for female age? SUMMARY ANSWER: Male ageing is negatively associated with clinical IVF/ICSI outcomes in couples with idiopathic infertility independent of female age. WHAT IS KNOWN ALREADY: The effect of male age on the outcomes of infertility treatments is controversial and poorly explored. In contrast, fertility is known to decline significantly with female age beyond the mid-30s, and reduced oocyte quality plays an important role. The negative effect of male age on sperm quality is largely associated with an increasing susceptibility to sperm DNA damage. Although increasing maternal age has been linked with poorer oocyte quality, studies on the effect of male age have disregarded the need to control for female age making it difficult to define clearly the role of male age in infertile couples. STUDY DESIGN, SIZE, DURATION: This retrospective cohort study analysed 2425 cycles of couples with idiopathic infertility selected from a total of 24411 IVF/ICSI cycles performed at Monash IVF in Australia between 1992 and 2017. The primary outcome was live birth and secondary outcomes were clinical pregnancy and miscarriage. PARTICIPANTS/MATERIALS, SETTING, METHODS: Couples with primary/secondary infertility who underwent IVF/ICSI cycles with male partners classified as normozoospermic were selected (inclusion criteria). Couples in which the female partner had endometriosis, tubal factors, polycystic ovarian syndrome, ovarian hyperstimulation syndrome, poor responders (<= 3 mature oocytes retrieved) and couples with more than 15 cumulus oocyte complexes retrieved or who used cryopreserved gametes were excluded. Binary logistic multilevel modelling was used to identify the effect of male age and female age on clinical outcomes after controlling for confounding factors. Male age and female age were examined as continuous and categorical (male age: <40, 40-44, 45-49, 50-54, >= 55; female age:<30, 30-34, 35-39, >= 40) predictors. MAIN RESULTS AND THE ROLE OF CHANCE: There was a negative effect of male age and female age on live birth as odds ratios (OR) with 95% CI for each additional year of age (OR-male age: 0.96 [0.94-0.98]; OR-female age: 0.90 [0.88-0.93] P<0.001). Potential interactions with male age such as type of treatment (IVF/ICSI), embryo transfer day (Day 3/Day 5) and female age did not have significant associations with outcomes (P>0.05). Secondary outcomes showed a significant reduction in the odds of clinical pregnancy (OR-male age: 0.97 [0.96-0.99]; OR-female age: 0.92 [0.89-0.94] P<0.001) and an increase in the odds of miscarriage with older age: male age (OR: 1.05 [1.01-1.08]; P=0.002); female age (OR: 1.11 [1.05-1.18]; P<0.001). Worse outcomes were associated with more cycles (clinical pregnancy-OR: 0.96 [0.93-0.99] P=0.03; live birth-OR: 0.96 [0.92-0.99] P=0.023) while more inseminated oocytes were associated with better outcomes (clinical pregnancy-OR: 1.06 [1.03-1.06] P<0.001; live birth-OR: 1.07 [1.04-1.11] P<0.001). Analyses for age categories showed a gradual worsening of clinical outcomes with increasing male age, with a significantly worse live birth and clinical pregnancy outcomes in males aged older than 50 years compared to males younger than 40 years (P<0.05). LIMITATIONS, REASONS FOR CAUTION: This study is limited to the information on confounding factors included. The study may also be limited in its generalizability to a wider population due the strict selection criteria. Age as a category could potentially result in residual confounding due to categorizing a continuous variable. WIDER IMPLICATIONS OF THE FINDINGS: This study provides information for counselling of couples with idiopathic infertility.