A boy tries to catch soap bubbles on the promenade of the Bund along the Huangpu River during a May Day holiday in Shanghai on May 1, 2019.

The world's largest country by population could hit a ceiling six years earlier than expected, a new report predicts. China's population is likely to peak in 2023, according to a study by online database company Global Demographics and analytics firm Complete Intelligence. The Chinese government had previously estimated that the country would hit its maximum population size in 2029. "What we see is the rate of growth slowing pretty, pretty quickly," said Tony Nash, chief executive and founder of Complete Intelligence. "People had expected peak population in China to be a decade away, when in fact, it's not," he said. "It's right around the corner." The decline in births is driven by a "maternity cliff," according to the report. The number of women of childbearing age in China — defined as aged 15 to 49 by the publishers — is set to fall from 346 million in 2018 to 318 million in 2023. With fewer women of childbearing age and fewer births per 1,000 women, the total number of newborns will drop as well. The study predicts that 13.3 million babies will be born in 2023, down from 15.2 million last year. China started easing its one-child policy in late 2013, and while those changes initially produced a boost in births, the effect may have worn off. That is, authors of the report wrote that Chinese mothers are no longer delivering on "pent up demand" for children since the policy was lifted to counter aging problems in the country.

The number of births per 1,000 women rose sharply from 45.6 in 2015 to 49.9 in 2016, the year where all Chinese couples were allowed to have two children. In 2018, the figure dropped drastically to 43.9. Total births fell 12 percent from 2017 to 2018. "China has stabilized its total population successfully," Clint Laurent, founder of Global Demographics said in a press release. "But delaying relaxation of the One Child Policy means it is now short of childbearing women." Complete Intelligence's Nash told CNBC's Street Signs: "The real issue ... is that every woman who will have a child before 2035 is already alive." "There's really nothing that the Chinese government can do to force more babies," he added. That is, unless each woman has "profoundly" more children, but that is "unlikely" as China gets wealthier, Nash noted.

The impact of China's peak population