Thinking of having a baby? Your children may mean more to the world than you think.

Hakuo Yanagisawa, Japan’s Minister of Health, Labour and Welfare, commented last month on a growing trend of precipitously falling birth rates-or total fertility rates-in the developed world.

“The number of women aged between 15 and 50 is fixed,” Yanagisawa said. “Because the number of birth-giving machines and devices is fixed, all we can do is ask them to do their best…although it may not be so appropriate to call them machines.”

Despite his rather bizarre depiction of women, Yanagisawa was raising a problem that faces nations including Taiwan, South Korea, Singapore and Canada.

The replacement birth rate is around 2.1, meaning an average of 2.1 children per woman are needed to maintain the current level of population-one for each parent and a little more to account for childhood mortality. Japan’s birth rate was 1.26 in 2005, a number thought to have fallen in the last year.

Europe faced a similar issue in the 1990s, when its birth rate hit 1.3. By enacting family-friendly legislature, such as longer paid maternity leaves for a third child, affordable childcare, and free nurseries, France managed to drive birth rates up to 1.8 child per mother, the current highest throughout Europe.

Japan and Singapore are ready to introduce similar policies to encourage family growth from childcare facilities in the workplace to more flexible working hours. Singapore has also sought to import a higher population by attracting talented immigrants.

Still, the declining birth rate trend is spreading. As Latin America and the Caribbean continue to develop economically, countries like Brazil now have birth rates of 2.3 to 4, a steep drop from the 6.0 it had in the 1960s. Likewise, Africa is seeing a slow decline in birth rate, from 6.9 in the sixties to 5.1 today.

Perhaps most the most dramatic changes have been seen in Asia. Newly-industrialized countries Taiwan and South Korea both have birth rates of 1.1, while Asia’s overall birth rate is 2.4. In India, the birth rate is slightly below 3.0, but the actual birth rate varies radically between the overpopulated, underdeveloped North and the more educated South.

While the U.S. has a birth rate of about 2.0, barely below the replacement rate, Canada’s birth rate is estimated to be 1.6. But Statistics Canada reports that even under the most modest population growth models, Canada’s immigrant-dependent population is not likely to fall in the near future.

Worldwide, the human population is still growing. The UN predicts 9.1 billion people will populate the world in 2050, up from the 6.5 billion who populate it today. But the rapid drop in the birth rates of developed nations may influence this figure dramatically.

With information from Statistics Canada, The Guardian, New Scientist, and the Population Reference Bureau.