The data is contained in the joint ‘Levels and Trends in Child Mortality’ report, which show that ever more and more women and newborns are surviving worldwide, but that one dies every 11 seconds, mostly from preventable causes.

According to the report, Portugal in 1990 registered 12 deaths of children under the age of five, but the figure fell to three in 2017, putting Portugal among the 30 countries in the world with the lowest rate, out of 172 countries analysed.

Japan and Iceland are the countries with the lowest mortality rate, with five deaths of under-5s per thousand live births, followed by Finland, Monaco and Sweden, each with six deaths per thousand, according to the report.

At the other end of the scale, Liberia has 174 deaths of under-5s per thousand live births, Mozambique has 159 and Sierra Leone 155.

The mortality rate for newborns (within 28 days of birth) in Portugal has also fallen sharply, from seven per thousand live births in 1990 to two per thousand in 2017, again placing Portugal among the best countries in the world on this indicator.

Japan, Estonia, Andorra, Iceland, Slovenia, Singapore and San Marino are the countries best placed here, with just one newborn death per thousand live births in 2011. In Pakistan, the country with the worst record on this front, there were 44 deaths per thousand live births that year.

According to the reports, since the year 2000, the rate of deaths of newborn children has almost been cut in half, while the deaths of pregnant women have been reduced by more than one third, mainly due to improvements in access to quality health services at affordable prices.

Estimates show that 6.2 million children under 15 died in 2018 and more than 290,000 women died due to complications during pregnancy or during childbirth in 2017. Of those children, 5.3 million died in their first five years of life, and almost half in the first month.

Women and infants are "more vulnerable" during and immediately after childbirth, with an estimated 2.8 million pregnant women and newborns having died last year – or one every 11 seconds – mostly of avoidable causes, according to the latest statistics.

"In all the world, the birth of a child is a cause for celebration,” commented UNICEF's executive director, Henrietta Fore. “However, every 11 seconds, the birth of a child is a family tragedy.”

She stressed that "a skilled pair of hands" can make the difference between life and death, by helping mothers during pregnancy and childbirth, with clean water, adequate nutrition or basic vaccines.

According to the study, one in every 137 women in sub-Saharan Africa is at risk of dying, while in Europe the figure is just one in 6,500.

Sub-Saharan Africa and southeast Asia account for about 80% of the deaths of pregnant women and children.

In spite of all this, the document states, "substantial progress has been made" in reducing the death of pregnant women, newborns and under-5s.

Since 1990, there has been a 56% reduction in the deaths of under-15s, from 14.2 million to, last year, 6.2 million.

The countries of East and South Asia recorded the greatest advances on this front, with an overall reduction of nearly 80% of the deaths of children under the age of five.

From 2000 to 2017, highlights the study, the rate of maternal mortality in the world decreased by 38%, with the reduction in South Asia as much as 60%.

East Timor, Bangladesh, Belarus, Cambodia, Kazakhstan, Malawi, Morocco, Mongolia, Rwanda and Zambia are among countries that have shown "substantial progress" in reducing their rates of maternal and infant mortality.

This success, the study reads, was mainly thanks to a "political will" to improve access to health services, along with investment in sanitation, and the introduction of free support to pregnant women and children under five, as well as the development of family planning services.