Stress before conception may influence offspring growth, CU Anschutz study finds
Research from the University of Colorado Anschutz suggests that stress experienced by a father before conception may influence an offspring’s growth by altering small molecular signals in sperm.
The study, published today in iScience, focuses on a tiny stress responsive molecule called let 7f 5p, found in sperm. This molecule increases under stress. Researchers found that it may help shape how an embryo develops in its earliest stages, which can later influence growth after birth.
The findings suggest that preconception stress may influence early development through biological signals in sperm, not changes to DNA.
What did the study find
In mice, scientists increased levels of let 7f 5p in fertilized eggs to mimic the biological effects of paternal stress. They found that male offspring exposed to higher levels of this molecule grew larger and developed longer bones. These changes occurred even though they ate normally.
What sperm are actually carrying
The findings suggest sperm carry more than genetic information. They also carry molecular signals shaped by life experiences, including stress.
“This study shows that sperm carry more than DNA,” said Tracy Bale, PhD, lead author and the Anschutz Foundation Endowed Chair in Women's Integrated Mental and Physical Health Research at the Ludeman Center at CU Anschutz. “They carry information about a father’s experiences that can shape early development and long-term health.”
Research team perspective
Study co-author Neill Epperson, MD, emphasized that the findings add to a growing body of work suggesting that preconception biology is influenced by lived experience and may have measurable effects on offspring development.
“Taken together with our prior work, these findings strengthen the evidence that stress biology in the germline is not fixed,” said Epperson, professor and chair of the CU Anschutz Department of Psychiatry and Bale’s partner on the studies. “It seems to change in response to life experiences in ways that can influence early development.”
How this fits into earlier research
This study builds on their earlier research showing that stress can change molecules in sperm and affect how offspring develop.
Their previous work found links between stress and changes in offspring brain development, behavior and metabolism. This new study adds evidence that the same biological system may also influence physical growth, including body size and bone development.
What kinds of stress may be involved
Researchers say ongoing or repeated stress before conception may play a role in these biological changes.
“For example, prolonged stress such as caring for a seriously ill family member, working in a high-pressure job or coping with financial strain could increase levels of this molecule in sperm. That molecule may subtly influence how a child’s body develops before birth,” said Bale. “It is like a father’s stress quietly nudges the body’s growth settings, with effects that show up later in life.”
What does this mean for prospective parents
The study highlights that health before conception may matter not only through genetics but also through biological signals influenced by life experience.
Researchers emphasize that managing stress, getting enough sleep, eating well and seeking support during difficult times may help support healthier biological conditions before conception.
“This research is about understanding that our experiences can have biological effects,” Bale said. “Taking care of ourselves before conception is an important part of planning for healthy children.”
Why this matters
The findings add to growing evidence that parental experiences before pregnancy can influence early development through molecular changes in sperm. The findings help researchers better understand how stress biology may influence development across generations.
Reference:
Jeng A, Creutzberg K, Feltrin A ... Elevated zygotic let-7f-5p alters developmental trajectories and sex-specific somatic growth, iScience, 2026.
