Pope Francis has expressed his regret that more couples today appear content to have cats and dogs, rather than children.
In his general audience on Wednesday, the Pope described the downward trend in birth rates across Western countries as a "demographic winter".
But he also expressed regret that couples choosing to have children may stop after only one or two.
He blamed the trend away from having children on "a certain selfishness" in society.
The Pope said that although there was "always a risk" in having children, it is "riskier not to have them".
"The other day, I spoke about the demographic winter there is nowadays, in which we see that people do not want to have children, or just one and no more," he said.
"And many, many couples do not have children because they do not want to, or they have just one — but they have two dogs, two cats. ... Yes, dogs and cats take the place of children."
The Pope then warned against "the denial of fatherhood or motherhood", which he said "diminishes us" and "takes away our humanity".
"It is riskier to deny fatherhood, or to deny motherhood, be it real or spiritual," he said.
"But denial, a man or woman who do not develop the sense of fatherhood or motherhood, they are lacking something, something fundamental, something important."
He warned that civilization itself would be diminished if birth rates continue to decline.
"Civilization becomes aged and without humanity because it loses the richness of fatherhood and motherhood," he said.
"And our homeland suffers, as it does not have children, and, as it has been said somewhat humorously, 'and now who will pay the taxes for my pension, if there are no children?'... [I]t is the truth."