We have long known that a pregnant woman\u2019s actions impact her unborn child. These impacts can even ripple outward into the child\u2019s life many years later. Bad habits like drinking and smoking can cause birth defects that last a lifetime and good habits like eating well can give a child a leg up in life. Evidence that the father\u2019s behaviors could affect an unborn baby, on the other hand, has been scarce. The child develops and grows inside the mother, so how could the father\u2019s health have any impact? New research says that it does, and it is related to sperm cells. Sperm Cells and Stress It seems obvious that a mother\u2019s stress could affect her child. They are, after all, sharing a body. How could Dad\u2019s stress make changes to an unborn baby? Through his sperm and the act of conception. According to new research, published in the Journal of Neuroscience, chronic stress can actually change sperm cells, and therefore, affect the resulting embryo, fetus and child. The research was conducted at the University of Pennsylvania\u2019s medical and veterinary schools. Professors and graduate students investigated the effects of stress on male mice and their offspring. By stressing out adult, male mice, the researchers found that the result was an epigenetic change in the sperm cells of those mice. Epigenetic means an outside factor\u2014like stress, for instance\u2014influences the expression of genes. Something like stress or drug abuse or trauma or any number of environmental factors can cause certain genes to be expressed or to not be expressed. Stressed Offspring In the case of the stressed-out mice, the epigenetic change caused the offspring mice to have blunted reactions to stress. When the offspring mice were exposed to stressful situations, in other words, their natural reactions were not quite what they should have been. They produced less of the stress hormone corticosterone \u2014 in humans, it's cortisol\u2014in response to stress than mice with dads that were not stressed. It may seem that producing less of a stress hormone is a good thing, but according to researchers, it is not. Any change in the normal stress pathway, whether that means producing more or less of the stress response hormone, means that an individual is not responding appropriately to stress. Not responding in the right way means that the individual, mouse or human could experience or develop psychiatric disorders. On the other hand, the researchers point out that the changes seen in the baby mice might be an attempt at evolutionary adaptation. If the father was stressed out, the low response in the mice offspring might be seen as preparation for being born into a stressful environment. Regardless, the changes in the stress response in the brain could have a very negative impact on a human child. What\u2019s Next? The findings of this latest research into a father\u2019s impact on his unborn child give scientists yet more information about how we develop mental illnesses. That a father\u2019s sperm can make changes in a baby\u2019s brain circuitry is a clue that can lead to further discoveries about the brain, its functioning, epigenetics, and how this is all related to mental health. The researchers found molecules present in the mice dads\u2019 sperm cells that probably were responsible for acting during fertilization. It could be these molecules that are the clue to how the pathway works from stressed father, to altered sperm, to affected child. If the researchers can sort that out and identify how the molecules act, they may be able to use them to prevent and treat disorders in the future. The takeaway lesson from this research for fathers-to-be is that their lifestyles affect their children even before they are born. Having chronic stress is bad for anyone\u2019s health, and in itself is a reason to relax and slow down. However, for those men that are stressed out and hoping to become fathers, there are now more reasons to cope with stress. If you are facing fatherhood with chronic stress, or you are facing motherhood with a stressed out partner, now is the time to get help. See a doctor for suggestions on how to bring down your stress levels. Take time from work to do more enjoyable activities. Try yoga or meditation and get more exercise. The more you can reduce stress, the better off both you and your future child will be.