Growth of the Fetus And Rectal Palpation
At day 18 to 20 the embryonic vessicle becomes large enough that it can now be detected by rectal palapation of the uterine horns and body. Prior to ultrasoundography, this was the main method to diagnose pregnancy in the mare. The following tables first describe major distinquishing structures used to determine pregnancy at increasing days in the mare and then a table of images and diagrams of embryos through day 50 of gestation.
Images of equine embryo development (day 18 - 50).