Pregnancy detection in mice using ultrasound

DIAGNOSTIC ultrasound has been used in almost all medical fields and is recognised as an increasingly important modality in a variety of clinical situations. The mouse is currently the most widely used animal in biomedical research (Marshall 2000). Diagnosis of pregnancy in experimental mice is possible at 12 to 14 days gestation, when abdominal distension is apparent. Mice with large litters may show distension slightly earlier (Kaufman 1989). Diagnosis of pregnancy at 7·5 days in experimental mice is currently performed by direct inspection of the uterine horns after laparotomy, with no routine utilisation of imaging techniques. The embryonic mouse is a ubiquitous model of mammalian development, due to the obvious benefits of a short gestation cycle, and genetic homologies with developmental genes in other mammals. Such models should yield further insight into the mechanisms responsible for human developmental and disease processes. Most previous investigations of the gestation period in the mouse have been invasive in nature.