Reference Manual 4
OB Reference
Gestational Age in the Dog
Standard GA: 65 days
Gestational Sac Diameter (GSD): MATOON
Reference: Mattoon JS, Nyland TG, Ovaries and uterus, In Nyland TG and Mattoon JS (eds),
Small Animal Diagnostic Ultrasound, 2nd ed, WB Saunders, Co, Philadelphia, 231-249, 2002.
* Less than 40 days
GA Equation
GA = (6 × GSD) + 20
Output Unit: d (days)
Input Unit: cm
Min Range: 0.1 cm
Max Range: 3.33 cm
Fetal Growth Equation
GSD = (MA x 7 – 20) / 6
Output Unit: cm
Input Unit: w (week)
Min Range: 1w
Max Range: 6w
Crown Rump Length (CRL): MATOON
Reference: Mattoon JS, Nyland TG, Ovaries and uterus, In Nyland TG and Mattoon JS (eds),
Small Animal Diagnostic Ultrasound, 2nd ed, WB Saunders, Co, Philadelphia, 231-249, 2002.
* Less than 40 days
GA Equation
GA = (3× CRL) + 27
Output Unit: d (days)
Input Unit: cm
Min Range: 0.1 cm
Max Range: 4.3 cm
Fetal Growth Equation
CRL = (MA x 7 – 27) / 3
Output Unit: cm
Input Unit: w (week)
Min Range: 1w
Max Range: 6w
Head Diameter (HD): MATOON
Reference: Mattoon JS, Nyland TG, Ovaries and uterus, In Nyland TG and Mattoon JS (eds),
Small Animal Diagnostic Ultrasound, 2nd ed, WB Saunders, Co, Philadelphia, 231-249, 2002.
* Less than 40 days
GA Equation
GA = (15× HD) + 20
Output Unit: d (days)
Input Unit: cm
Min Range: 1.34 cm
Max Range: 3 cm
Fetal Growth Equation
HD= (MA x 7 – 20) / 15
Output Unit: cm
Input Unit: w (week)
Min Range: 5w
Max Range: 10w
Body Diameter (BD): MATOON
Reference: Mattoon JS, Nyland TG, Ovaries and uterus, In Nyland TG and Mattoon JS (eds),
Small Animal Diagnostic Ultrasound, 2nd ed, WB Saunders, Co, Philadelphia, 231-249, 2002.
* Less than 40 days
GA Equation
GA = (7× BD) + 29
Output Unit: d (days)
Input Unit: cm
Min Range: 1.58 cm
Max Range: 5.21 cm
Fetal Growth Equation
HD= (MA x 7 – 29) / 7
Output Unit: cm
Input Unit: w (week)
Min Range: 5w
Max Range: 10w
Head and Body Diameter (HD_BD): MATOON
Reference: Mattoon JS, Nyland TG, Ovaries and uterus, In Nyland TG and Mattoon JS (eds),
Small Animal Diagnostic Ultrasound, 2nd ed, WB Saunders, Co, Philadelphia, 231-249, 2002.
* Less than 40 days
GA Equation
HD_BD_Dog = (6× HD) + (3× BD) + 30
GA = HD_BD_Dog ×1
Output Unit: d (days)
Input Unit: cm
Min Range: 40 cm
Max Range: 65 cm
Reference Manual 5
Gestational Age in the Cat
Standard GA: 65 days
Gestational Sac Diameter (GSD): ZAMBELLI
Reference: Zambelli D, Castagnetti C, Belluzzi S, Bassi S, Correlation between the age of the
conceptus and various ultrasonographic measurements during the rst 30 days of pregnancy in
domestic cats (Felis catus), Theriogenology, 57, 1981-1987, 2002.
* Less than 30 days
GA Equation
GA = (1.0901 × GSD × 10) -0.9372
Output Unit: d (days)
Input Unit: cm
Min Range: 0.1 cm
Max Range: 2.83cm
Fetal Growth Equation
GSD = (MA x 7 + 0.9372) / 1.0901
Output Unit: mm
Input Unit: w (week)
Min Range: 1w
Max Range: 5w
Crown Rump Length (CRL): ZAMBELLI
Reference: Zambelli D, Castagnetti C, Belluzzi S, Bassi S, Correlation between the age of the
conceptus and various ultrasonographic measurements during the rst 30 days of pregnancy in
domestic cats (Felis catus), Theriogenology, 57, 1981-1987, 2002.
* Less than 30 days
Reference Manual 6
GA Equation
GA = (1.0099 × CRL × 10) -0.03378
Output Unit: d (days)
Input Unit: cm
Min Range: 0.1 cm
Max Range: 3 cm
Fetal Growth Equation
CRL = (MA x 7 + 0.03378) / 1.0099
Output Unit: cm
Input Unit: w (week)
Min Range: 1w
Max Range: 5w
Head Diameter (HD): MATOON
Reference: Mattoon JS, Nyland TG, Ovaries and uterus, In Nyland TG and Mattoon JS (eds),
Small Animal Diagnostic Ultrasound, 2nd ed, WB Saunders, Co, Philadelphia, 231-249, 2002.
* Less than 40 days
GA Equation
GA = (25× HD) + 3
Output Unit: d (days)
Input Unit: cm
Min Range: 1.48 cm
Max Range: 2.37 cm
Fetal Growth Equation
HD= (MA x 7 – 3) / 25
Output Unit: cm
Input Unit: w (week)
Min Range: 5w
Max Range: 9w
Head Diameter (BD): MATOON
Reference: Mattoon JS, Nyland TG, Ovaries and uterus, In Nyland TG and Mattoon JS (eds),
Small Animal Diagnostic Ultrasound, 2nd ed, WB Saunders, Co, Philadelphia, 231-249, 2002.
* Less than 40 days
GA Equation
GA = (11× BD) + 21
Output Unit: d (days)
Input Unit: cm
Min Range: 1.73 cm
Max Range: 3.59 cm
Fetal Growth Equation
HD= (MA x 7 – 21) / 11
Output Unit: cm
Input Unit: w (week)
Min Range: 5w
Max Range: 9w
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