"Millions of families lack access to nutritious food, safe water, sanitation, or a secure and healthy environment to grow and bond," UNICEF Executive Director Henrietta Fore said in a press release.
"Along with the immediate, obvious dangers, the long-term impacts of such a start in life are potentially catastrophic."
Prolonged or repeated traumatic experiences can affect children's learning, behaviour, and physical and mental health.
A UNICEF worker in Yemen saw children "so malnourished and traumatized they detach emotionally from the world and people around them, causing them to become vacant and making it impossible for them to interact with their families," according to the press release.
The organization said parents in conflict-affected areas "desperately need more support to help them and their children cope with the devastation they face."
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