FERRARA, Italy — On a recent night at the Blue Elephant recreation center here, a clutch of parents watched adoringly as dozens of 3- and 4-year-olds sprinted through a colorful playroom, bounced on the cushioned floor or doodled on drawing pads, aglow with creative pride.

It was Italy as outsiders still imagine it: child-worshiping and family-loving.

But there was something wrong with the picture. Most of the parents were gazing at one, and only one, child.

That was true of Gianluca Valenti, who said that giving his son any siblings would be too exhausting and expensive, and of Barbara Lenzi, who said that more than one child "doesn't seem to make sense."

It was also true of Rosa Andolfi, who responded to a question about having an additional child as if a vampire were near.

"Basta!" Ms. Andolfi more or less yelped, then made a cross with her index fingers and thrust it forward.

That gesture was not just funny but telling; it touched on an increasingly worrisome reality for Italy and other European countries whose fertility rates have plummeted over the last decades, shifting one-child families close to the statistical norm.

In Spain and Sweden, Germany and Greece, the total fertility rate — or the average number of children that a woman, based on current indicators, is expected to give birth to — was 1.4 or lower last year, according to the World Health Organization.

In no West European country did the rate reach 2.1 — the marker that, demographers say, means an exact replenishment of the population. By contrast, the United States had a 2.0 rate, which demographers attribute to greater immigration.

While that trend has been evident for many years, its slow-building consequences are now coming into starker relief, as more West European countries acknowledge and take new steps to address the specter of sharply winnowed and less competitive work forces, surfeits of retirees and pension systems that will need to be cut back deeply.

In Italy, where the fertility rate last year was 1.2, according to the health organization, Labor Minister Roberto Maroni has announced that the cost of the state pension system will need to be reduced. Mr. Maroni said the government would offer incentives, which he did not specify, to keep people at work past the minimum retirement age of 57.

The United Nations recently published data suggesting that the population of Spain could decline to about 31.3 million in 2050 from about 39.9 million now. According to the World Health Organization, Spain's fertility rate last year was 1.1, the lowest in Western Europe.

Many provinces in Italy's wealthy, well-educated north have rates well below that.

The rate in the province of Ferrara, which includes the city of Ferrara, has been under 0.9 for each of the years since 1986 that Italy's National Institute of Statistics kept track.

Ferrara officials talk about the dearth of young children in the streets, the closing of elementary schools over the last decade and a pervasive sense that something is missing.

"There's a lack of energy," Deputy Mayor Tiziano Tagliani said in a recent interview here. "The society is colder without children."

Nationwide, Italy's fertility rate has been so low for so long — under 1.5 since 1984 — that the country offers an especially good glimpse into the dimensions and dynamics of the trend.

For example, Italy now has the world's oldest population. The percentage of people 60 or older is 25, compared with 16 percent in the United States, according to the population division of the United Nations.

The division's experts project that by 2050, if current trends hold, 42 percent of Italy's population will be 60 or older.

Antonio Golini, a professor of demographics at the University of Rome, Sapienza, said that would be "unsustainable, from a cultural and even psychological point of view."

That sense of alarm was reflected in Pope John Paul II's first-ever address to the Italian Parliament in November. The pope said "the crisis of the birthrate" in Italy was a "grave threat that bears upon the future of this country."

In Italy, as in other West European countries, the low fertility rate is interwoven with an array of other issues — immigration, for one. While many people and many politicians in Europe would like to clamp down on the rising tide of new arrivals over the last decade, they may be forced to accept it, simply to fill jobs and maintain levels of productivity.

Europe stands out as the continent with the lowest fertility rates. The numbers are now starkest in East European countries like Bulgaria, Latvia and Ukraine, each of which had a rate of 1.1 in 2001, according to the World Health Organization. (Its figures sometimes differ slightly from those of individual countries, but provide a yardstick.)

But the trend hit Western Europe earlier, and has had more time to produce hand-wringing and soul-searching. Apart from welcoming more immigrants, no one knows precisely what to do.

Many governments have expanded tax breaks for parents, child care alternatives or maternity and paternity benefits, acknowledging that a high cost of living and more women in the work force can be obstacles to large families. In some of those countries, like France, the fertility rate has nudged slightly upward.

Spain is considering a variety of ways to address those obstacles: cheaper utility bills for large families; assistance for young couples who are trying to afford homes; the creation of hundreds of thousands of new preschools and nursery schools; and longer hours for existing schools, an accommodation for working parents.

Although the Italian government provides mothers with nearly full salary compensation for about a half-year of maternity leave, the city of Ferrara, like several other north Italian cities, added benefits that kick in after that period. They include cash supplements of about $350 a month for mothers who want to stay at home an additional nine months. Ferrara also has pumped millions of dollars into nursery schools and child care centers like the Blue Elephant.

But Italy's low fertility rate persists, suggesting that the reasons go well beyond the arithmetic of salaries and schedules.

"People are studying longer, and thus are finding work later, when there is work, and then are marrying later, which doesn't necessarily mean having a baby anymore," said Valerio Terra Abrami, head of the department of social statistics for Italy's National Institute of Statistics.

Contraception and abortion are more readily available. Divorce is more common.

Moreover, decades of prosperity have altered people's assumptions and expectations. Older people once poised to look after grandchildren now pursue other activities and travel more. As for would-be parents, their attachments to leisure time, conveniences and indulgences do not easily accommodate multiple children — or sometimes, for that matter, any children at all.

"It's never been at the top of my list," said Teresa Ginori, 41, a fashion magazine consultant who lives outside Milan. "It's never been in the top 200 things."

Ms. Ginori and many women she knows have never married, in part, she said, because of a facet of Italian life that she cited as one possible explanation for the especially low fertility rate here.

Many Italian men, she said, live with their mothers into their 30's. When they marry, they are not prepared to help out at home in ways that take pressure off women, especially if those women want to have children.

"Even the most open-minded guy — if you scratch with the nail a little bit, there's the mother who did everything for him," she said. "I hate the mothers of these men. These mothers are a disaster."

Parents also seem to feel that they owe more opportunities to the children they do have, a conviction that discourages large families.

That partly explained the prevalence of only children in Ferrara, where one-child parents at the Blue Elephant center mentioned siblings who had also stopped at one child. The center's coordinator, Monica Viaro, 37, has only one child, an 8-year-old son.

Ms. Andolfi, 32, who has a 3-year-old son, said a second child would limit her son and limit the baby.

She conceded that her family's definition of what it needed was expansive.

"The cellphones aren't enough and the televisions aren't enough," she said. "It's a little selfish."

Ms. Lenzi, 32, who is also part of a two-career couple, said she liked to read to her 3-year-old son, adding, "It doesn't make sense to have three just to tuck them in at night and say, `Ciao, stella,' and that's it."