Preliminary study of the ultrasonographic diagnosis of pregnancy and fetal development in the dog.

A total of 18 dogs were examined by ultrasound during their gestation period. At gestational day 7, a uterus indicative of possible pregnancy was observed. At gestational day 10, the embryo was observed. Fetal and cardiac activities appeared at 28 days. Rapid increases of the crown-rump length and biparietal diameter occurred between the 5th and the 6th weeks of gestation and of the body diameter between the 4th and 5th weeks and again between the 6th and the 7th weeks of gestation.