Declining fertility rates leading to a 'baby bust'
By Jennifer Cockerell, Press Association Health Correspondent
Declining fertility rates around the world are leading to a "baby bust" in many countries including the UK, health experts have warned.
Globally fertility rates, which represent the average number of children a woman delivers over her lifetime, have declined since 1950 and in 91 nations, rates are now not high enough to maintain current population levels.
The large-scale study, published in the Lancet, found that in 2017, 91 countries (including the UK, Singapore, Spain, Norway and South Korea) had rates lower than two and were not maintaining their current population size.
Meanwhile 104 nations were seeing population increases due to their high fertility rates (rates above two).
The lowest rate was in Cyprus where, on average, a woman now gives birth to one child throughout her life, while the highest was in Niger, with a total fertility rate of seven children.
The fertility rate in the UK is 1.7, which is similar to most Western European countries.
Dr Christopher Murray, director of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, said: "These statistics represent both a 'baby boom' for some nations and a 'baby bust' for others.
"The lower rates of women's fertility clearly reflect not only access to and availability of reproductive health services, but also many women choosing to delay or forgo giving birth, as well as having more opportunities for education and employment."
He also told the BBC: "We've reached this watershed where half of countries have fertility rates below the replacement level, so if nothing happens the populations will decline in those countries.
"It's a remarkable transition.
"It's a surprise even to people like myself, the idea that it's half the countries in the world will be a huge surprise to people."
The figures come from the annual Global Burden of Disease study (GBD), which provides estimates for around 280 causes of death, 359 diseases and injuries and 84 risk factors in 195 countries and territories worldwide.
The study is coordinated by the IHME and involves more than 3,500 collaborators from across more than 140 countries and territories.
Other findings include that more than half of all global deaths in 2017 were caused by just four risk factors, high blood pressure, smoking, high blood glucose, and high body mass index (BMI).
High blood pressure was the leading risk, accounting for 10.4 million deaths, followed by smoking (7.1 million deaths), high blood glucose (6.5 million deaths), and high BMI (4.7 million deaths), amounting to 51.5% or 28.8 million out of 55.9 million deaths worldwide in 2017.
Professor John Newton, director of health improvement at Public Health England and GBD collaborator, said: "With many of the health issues that place the biggest burden on the UK's health service being substantially preventable, this is yet another reminder that prevention must be the centrepiece of any future plans to protect the health of the nation and the NHS.
"It also shows that new challenges are emerging all the time and we, individuals and governments, cannot take the health of the public for granted."