Children whose fathers were killed or seriously wounded in the First World War had their own lives shortened by a year on average, research has shown.
Life expectancy was reduced by more than two years for those who became fatherless while still in their mother's womb.
The explanation is still being investigated, but experts believe it to be linked to the effects of psychological stress on the children and their mothers.
According to some experts, much of our susceptibility to disease in adulthood may stem from what happens to us very early in life.
The French study aimed to investigate the potential impact of early negative experiences, or "early life adversities" (ELAs), on children born during the First World War.
A team from the French National Institute of Health and Medical Research (Inserm) identified more than 4,000 children born between 1914 and 1916 whose fathers had either been killed in the trenches or severely injured.
Each child was matched with another - a "control" - who was born at the same time in the same district, but did not experience the tragedy of having a war victim father.
Compared with the control subjects, children whose fathers had been killed or badly wounded in the war lost an average of one year of life expectancy.
The effect was greater for those whose fathers died while their mother was pregnant. Their adult lives were typically shortened by 2.2 years.
Lead researcher Nicolas Todd, from Kremlin-Bicetre Hospital in Paris, said: "The next step in the study will be to determine the cause of death for those having suffered ELA. This will shed light on the mechanisms involved.
"We know that deregulation of the stress response is commonly found on animal models of ELAs, so it will be interesting to see if any evidence of this can be seen in the causes of death in the French cohort. It may give us further insight into the long-term effects of ELA."
The research was presented at the annual meeting of the European Society for Paediatric Endocrinology taking place in Paris.