Couples in East China's Shandong province are the most active about having a second child, Beijing Evening News reports.

Shandong had implemented strict family planning before, so great potential may be unleashed after relaxation of the one-child policy, said the newspaper.

A one-percent national sample census in 2015 found first-borns accounted for 43.8 percent of Shandong's new births, while second children made up 52.2 percent, making it the only province with a second-child birth rate exceeding 50 percent. It also had the highest birth rate for second and more children in the country.

"Basically, provinces with larger populations also tend to have more births," said Yuan Xin, professor of population research at Nankai University. "Provinces with a high level of urbanization or that are economically better-off register fewer births, and the three northeastern provinces apparently saw fewer births."

Guangdong and Henan also had high second-child birth rates. Guangdong is the only province in China with a population of more than 100 million, while Shandong and Henan have a population of between 90 million to 100 million.

Three years ago, China began a policy that stated if either parent is an only child, their child is eligible to have two children of their own. Some 1.91 million eligible families then filed application papers for another child, 25 percent of them from Shandong.

On January 1, 2016 China further eased its policy to allow all couples to have two children. There were 17.86 million newborns in 2016, of which second children accounted for 45 percent.

He Dan, a senior researcher of population, said more than 60 percent of couples nationwide unwilling to have a second child cited economic or child care concerns.