Paternal age plays a critical role in IVF success -- even when using eggs from young, healthy donors -- a study has found.
At the 41st ESHRE Annual Meeting, researchers reported that male partners over 45 have higher miscarriage risks and lower live birth chances during IVF with donor eggs.
The research, spanning 1,712 donor egg IVF cycles conducted between 2019-2023 in Italy and Spain, aimed to isolate the impact of paternal age by controlling for maternal variables.
All cycles involved fresh oocytes (immature eggs found in the ovaries) from young donors (average age 26.1), frozen sperm from male partners and a single blastocyst embryo transfer. The average age of female recipients was 43.3.
When results were analyzed, stark differences emerged between the two paternal age groups: Miscarriage rates were 23.8 percent among couples with male partners over 45, compared to 16.3 percent in those with younger male partners.
"It was genuinely surprising to see how strongly paternal age affects miscarriage and live birth rates, even in oocyte donation programs," lead author and embryologist Maria Cristina Guglielmo of Eugin Italy told Newsweek.
Live birth rates dropped to 35.1 percent in the older paternal group, versus 41 percent for those aged 45 or younger.
"This challenges the common perception that maternal factors are the primary drivers of reproductive success and highlights the need to pay more attention to paternal factors in fertility," said Guglielmo.
She explained that biological changes in sperm linked to aging -- such as increased DNA mutations, abnormal chromosome counts, DNA fragmentation and altered epigenetics -- can compromise embryo development and raise miscarriage risk.
"Together, these factors affect both the genetic integrity and the functional quality of sperm which can impair embryo development and contribute to a higher risk of miscarriage," she added.
Importantly, the study only included first embryo transfers and excluded repeat cycles, allowing for a clearer comparison.
According to Guglielmo, this strengthens the evidence that paternal age is not just a minor variable but a significant factor in reproductive outcomes.
"Our hypothesis is that time does not change the ability of sperm to produce embryos; however, some genetic defects in sperm only become apparent later in the process, potentially leading to adverse effects on embryo development and contributing to negative selection outcomes in the fetus," she said.
For couples who are considering starting a family later on in life via IVF, Guglielmo advises consulting with a fertility specialist early to understand how paternal age might affect chances and explore all available options.
"All women know how miscarriage is associated with mother’s age; however, it's time to inform couples about father’s age importance especially during pregnancy in order to evaluate prenatal screening," she said.
"Being well-informed and proactive can help couples make the best decisions for their family-building journey and improve their chances of achieving a successful and healthy live birth."Guglielmo, M.C., et al. (2025). Advanced paternal age affects miscarriage and live birth outcomes following the first transfer in oocyte donation cycles. Human Reproduction.