Serial ultrasonographic examinations were daily performed from 15 days after ovulation until parturition to determine the growth curve of gestational structures in pregnant Maltese, Yorkshire terrier, Shih-tzu, and Miniature Schnauzer bitches, respectively. Gestational age was timed from the day of ovulation (day 0), which was estimated to occur when plasma progesterone concentration was first increased above 4.0 ng/ml. The inner chorionic cavity diameter were significantly and linearly relative to gestational age especially days 20 to 40, and the fetal head diameter were significantly and linearly relative to gestational age especial1y day 40 to parturition. These results indicate that inner chorionic cavity diameter were the most accurate for estimating gestational age before day 38 of gestation and the fetal head diameter were after day 38 of gestation.

• 오기석(전남대학교 수의과대학)
• 김방실(전남대학교 수의과대학)
• 박상국(전라남도 축산기술연구소)
• 박철호(전남대학교 수의과대학)
• 김재홍(전남대학교 수의과대학)
• 문병권(전남대학교 수의과대학)
• 김희수(전남대학교 수의과대학)
• 이주환(전남대학교 수의과대학)
• 박인철(강원대학교 수의(학부)대학)
• 김종택(강원대학교 수의(학부)대학)
• 서국현(전남대학교 수의과대학)
• 손창호(전남대학교 수의과대학)