Noninvasive Ultrasound Monitoring of Embryonic and Fetal Development in Chinchilla lanigera to Predict Gestational Age: Preliminary Evaluation of This Species as a Novel Animal Model of Human Pregnancy

Table 5

Best-fit regression coefficient and standard error for the three groups of variables.

Gestation time	Model	Set of parameters	Coefficient	Standard error
T1–T3	1	Placental thickness	2.54	0.15	<0.0001
		Constant	0.007
		T2-T3	2	Heart rate in beats per minute	−0.009	0.001	<0.0001
Crown-rump length	0.30			0.03	<0.0001
Constant	3.19
T2–T4	3	Head diameter	1.26	0.06	<0.0001
		Heart rate in beats per minute	−0.004	0.001	0.0008
		Constant	2.34

Model 1 uses placental thickness to predict the gestational age from T1 to T3. Model 2 uses HR and CRL to predict gestational age from T2 to T3. Finally, model 3 uses HD and HR to predict gestational age from T2 to T4.