A UK institute has used ultrasound to more accurately pinpoint pregnancy in mice, which could lead to a reduction in the numbers used for breeding in research.

The Biological Services Unit, of the Medical Research Council (MRC) Laboratory of Molecular Biology (LMB), introduced the ultrasound machines because it is important to detect the point of pregnancy during research – just one day’s difference to the 20-day gestation (pregnancy) period of mice can significantly alter the embryo.

Early-stage mouse embryos are used, for example, to study development and traditionally, pregnancy in mice has been determined through visual and physical checks, but this can be subjective and prone to error.

By using ultrasound scans, technicians can more accurately check for the key signs, as well as identify which mice are not actually pregnant, so they can be bred again – therefore helping to reduce the numbers used in breeding.

In addition, the team found that the ultrasound could be carried out simply by holding the mice down, without the need for anaesthesia, and took less than a minute. The mice also did not show any distress or changes in behaviour afterwards.