It could end the waiting game for pregnant women - and save the NHS millions.

Wouldn't it be great if you could predict when labour was going to start? No more fruitless dashes to hospital for false alarms. No more friends ringing to ask, "have you had it yet?"

Thanks to a new gadget designed by a team of British doctors, you may be able to do just that. The Prediction of Labour Onset device (POLO) uses electrical signals to give three to five days' advance warning of labour starting. And while it may help superwomen arrange their diary around childbirth,being able to predict the onset of labour can also save the lives of premature babies.

The POLO works by recording electrical signals that pass across the uterine muscle - these occur during pregnancy and become more frequent as labour approaches. The signals are then transmitted through electrodes held in place by a belt against the abdomen. Using a database of electrical activity measured in pregnant women across the world, the signals are compared and analysed to predict when labour could occur. POLO can be used from 32 weeks onwards.

John Gilmour, head of research of IMVD the scottish medical company behind POLO, explains: "A pregnant woman would take readings over several days, for about 10 minutes a day with the belt in place, to record electrical signals coming from the uterus. The software on the instrument interprets those signals and gives an advance warning - from three to five days - of when labour is about to start." While POLO can be used in hospitals, it is designed to be used in the home, saving valuable hospital space and giving anxious would-be mothers peace of mind. "The major thing that can be achieved with POLO is that we won't have about half of all women being admitted to hospital, with a false expectation that they're in labour and about to give birth. It could save the NHS millions."

It's not just expectant mothers and the NHS that POLO can help. One of the most dangerous risks for a baby is being born prematurely. The first hours of life for premature babies are critical - especially the first hour. As Amy Edmunds, spokeswoman for the premature baby charity Bliss explains, knowing the date of labour in advance could greatly improve the chances of survival of premature babies. "If an expectant mother gets an indication that she might give birth prematurely, that buys time. There are only certain units in the UK that are able to give care at the appropriate level. With advance warning, they can be ready." While Edmunds is optimistic about POLO, she has some reservations. "There's still no substitute for increased funds and increased staffing in hospitals - this device won't solve those problems."

Labour is notoriously difficult to predict, says Sally Marchant, a midwife and editor of, a website for maternity healthcare professionals. "Nobody knows why labour starts. We know it relates to hormonal changes and the body having a predetermined length for a pregnancy, but nobody knows the trigger." There are several methods that are currently used to estimate when labour will begin. "The most reliable way is to see what the cervix is doing. The cervix gets shorter and shorter during pregnancy- and the uterus shows signs that it's getting ready," says Marchant. "The other sign is that the baby shifts down in the pelvis. Even then, you could still be waiting for days."

However, Marchant has concerns about the POLO. "What wavelengths do they use to measure?People have concerns about mobile phones, WiFi and scanners, so is this safe?" Her other worry is that trying to pin down something as unpredictable as labour is unhelpful to pregnant women. " It sets up unrealistic expectations. It doesn't help them to understand how erratic labour is - a key concept if you're going to get through it."

At present IMVD is awaiting funding to convert the POLO prototype into a consumer-ready product, but it could be on the shelves in the UK in as little as a year to 18 months. Until then, mothers-to-be will have to rely on the tried, trusted and tested methods that doctors have always used to help schedule a birth.

Other ways to predict labour

* Baby heartbeat monitor

Monitoring is done using two electronic sensors, one placed on the top of the stomach, and one over the baby's heart. Each is attached to a wire, which is in turn attached to a machine. The machine gives a digital read-out of the baby's heartbeat. This figure changes according to the proximity of labour.

* Cervix

In preparation for labour, the cervix shortens and softens. This is sometimes referred to the "ripening of the cervix" or effacement. By the time a woman is ready for labour, her cervix will have stretched from around 1 inch in width to paper thinness. Before labour the membranes of the cervix rupture, releasing fluid - known as the waters breaking (usually the onset of labour).

* Baby moving down the pelvis

Babies usually engage - descend into the pelvis - before labour starts. This is also known as "lightening". The baby drops lower in the belly and settles deep in the pelvis. For first-time mothers, lightening can occur a few weeks before the baby's birth; for second-timers it may take place only a few hours labour begins.

* Pineapple

An old wives' tale says that eating pineapple helps to ripen the cervix. The enzymes in pineapple allegedly help to soften the connective tissue of the cervix. It's a long shot, but some swear it speeds up the onset of labour.