Monitoring the Foetal Phase of Gestation in the Queen With a 12.5-MHz Ultrasound Probe and Prediction of the Parturition by Combining the Measurements of Head and Abdominal Diameters.

Ten gestations in six domestic shorthair cats (Europeans) were monitored daily during the foetal phase of gestation, from the 28th day after the first mating until parturition, using ultrasound with a 12.5-MHz probe. The development of the various organs over this period was recorded. The diameters of the head (HD) and abdomen (AD) were measured. Skeletal calcification visible on ultrasound occurred in a defined order between the 34th and 40th day of gestation. During the last 30 days of gestation, there was a significant correlation between HD and days before parturition (DBP) (r(2)  = 0.99) and between AD and DBP (r(2)  = 0.98). The following equations were obtained: DBP = -2.10*HD (mm) + 50.74; DBP = -1.01*AD (mm) + 42.19. The confidence intervals were stable over the last 30 days of gestation. For the HD, the confidence interval was ±1 day in 53% of cases and ±2 days in 85% of cases. For the AD, the confidence interval was ±1 day in 45% of cases and ±2 days in 77% of cases. A table obtained by combining the HD and AD measurements made it possible to estimate the date of parturition within 2 days with a reliability of over 85%.