Speaking at a conference on Italy's derth of babies, Pope Francis said polls showed most young people wanted to have children, but were worried about the rising cost.
"Their dreams of a new life, the seeds of the country's rebirth, come up against a demographic winter that is cold and dark," the pope said.
"For the future to be good, we need to look after families, especially young families, who are beset by worries that risk paralysing their life plans. I am thinking of the fears caused by the increasingly unaffordable costs of raising children.
The sharp fall in 2020 in the number of babies born in many countries has been blamed on the stress and uncertainty generated by COVID. But the longer-term fertility trends across much of the developed world has been in decline for some years.
The pope also took aim at young people, saying some role models set the wrong example by being obsessed over their appearance and not being willing to make the sacrifices needed to raise a family.
"Staying young does not come from taking selfies and touch-ups, but from being able to look into the eyes of your children one day," he said.