The lives of tens of thousands of new mothers around the world could be saved by a simple, hand-held, British-made device costing only £12, which runs on a mobile-phone charger and is set to be introduced in hospitals across Africa, India and Pakistan.
Invented by doctors at one of London's leading hospitals, the device is the first in the world that can detect whether a woman is likely to go into shock after blood loss during childbirth.
Using a simple traffic-light system, it can also alert healthcare workers in rural communities when a pregnant woman's blood pressure is dangerously high - ensuring that she can be moved to hospital for life-saving care.
Death in childbirth is now extremely rare in the UK and other rich nations but in developing countries it is responsible for nearly 300,000 lives lost every year.
Experts said the device, known as the Microlife Vital Signs Alert (VSA), which is easy to use and can be charged using a USB cable, could play the crucial role of identifying women most in need of help - described by one leading obstetrician as the "holy grail" of maternal healthcare in the developing world.
The team who developed it, led by Professor Andrew Shennan, a consultant at Guy's and St Thomas' NHS Foundation Trust and professor of obstetrics at King's College London, estimates that if rolled out around the world, it could cut maternal mortality rates by 25 per cent - or 70,000 lives every year.
Backed by a $US1 million grant from the Bill and Melinda Gates Foundation, production of the device is accelerating. Last month around 2,500 were shipped out to clinics in Pakistan, Mozambique, India and Nigeria, and the US health charity Jhpiego has ordered 5,000 devices for its projects in Asia, Africa and the Caribbean.
High blood pressure during pregnancy can be an early-warning sign of pre-eclampsia, which is potentially fatal for mother and baby. In the UK, regular blood pressure checks identify those at risk, who are then carefully monitored and given medication. But in more remote towns and villages in the developing world, stretched health workers may miss warning signs. The Microlife VSA solves this by instantly alerting workers to dangerous BP readings.
Also, by automatically dividing the systolic blood pressure by the pulse rate the device highlights a "shock index". If a woman's shock index is high - revealing dangerous levels of blood loss - it shows a red light.
Andrew Weeks, consultant obstetrician at Liverpool Women's Hospital, and professor of international maternal health at Liverpool University, said it could provide a vital missing link in busy, under-resourced wards.
"The difficulty is trying to work out who are the sick mothers," said Professor Weeks, who has worked at the Mulago Hospital in Kampala, Uganda, and also set up a medical unit in the town of Mbale in the east of the country.
"The identification of those critically ill ones is one of the holy grails of medicine. The beauty of it is that it interprets it for you and categorises into red, amber or green."
For inventor Professor Shennan, the device is the culmination of 20 years' work. "We're very proud of this device," he said. "Not only can it accurately detect when a woman is in danger from high blood pressure or shock, but it also indicates to untrained people when to act on this. I use it in my NHS clinic, as it is superior to most existing devices for measuring blood pressure."
Jeffrey Smith, maternal health director at Jhpiego, the international charitable wing of Johns Hopkins University, described the device as a "really important advance". "It allows us to both improve the quality of care and increase the accessibility of care in a really remarkable way."