Pregnant women and midwives could benefit from a new tool designed to make water births safer and easier.

Researchers have invented an illuminated, adjustable mirror that can be used under water when a baby is being born. The device is the first of its kind and has been developed by a team from the University of Edinburgh and Loughborough and Heriot-Watt universities.

The mirror, which has lights around its frame, is mounted securely on a flexible pole. Its design makes it easier for midwives to see when a baby's head crowns - the moment when the head first becomes visible. As the baby's head crowns, midwives assist the infant's entry into the water. Midwives currently have to bend over the side of a pool and, with one hand, hold a mirror under the water to look for the baby's head crowning, while shining a torch above with the other hand. Researchers say that although this approach is safe, the new tool would improve the process for midwives - as they would no longer need to use two instruments, nor adopt an awkward position for a long time. It could also make having a water birth more pleasant and dignified for women, experts add.

Around 48,000 women in the UK have a water birth every year. Experts say that giving birth in a water pool is an effective form of pain relief and helps many women to feel in control during labour.

Researchers now hope to secure further funding to manufacture the mirror so that clinical trials to test it can begin.

The mirror has been developed with midwives at NHS Lothian Birth Centre in Edinburgh, and engineers and product designers at Heriot Watt University and Loughborough University. It is funded by the Edinburgh and Lothians Health Foundation, Tommy's the baby charity and the University of Edinburgh. It has also had the support of Edinburgh BioQuarter.

Project leader, Dr Fiona Denison, senior lecturer and honorary consultant in Maternal and Fetal Medicine at the University of Edinburgh's Tommy's Centre / Medical Research Council Centre for Reproductive Health, said: "We believe that our tool addresses an unmet clinical need and will help both mothers having water births and midwives who care for them. This prototype has been designed by midwives, for midwives."

Sheonagh Brook-Smith, lead midwife for the Lothian Birth Centre added: "It is important to try to create a relaxed and calm atmosphere when a woman is in labour. Sometimes, as a midwife you feel like you need to disrupt this to try and gain a clear view. My colleagues and I are excited about the prospect of an instrument that gives you a clear picture of what's happening without interruption."