An official in China's biggest city is calling on families to have more children as far fewer people than expected take advantage of a rule change that lets more households bear a second child.

The Qianjiang Evening News reported this week that Fu Tan of Shanghai's family planning commission said only 5 percent of women of child-bearing age in the city had applied to have a second child. The report said 90 percent of women of child-bearing age were eligible to have another child.

China's birth rate is among the lowest of developing countries, nearly four decades after the country restricted most urban couples to having one child.

China modified the rule in late 2013 to let additional households have a second child, but few have applied under the change.