Table 4. Multivariate ridge regression analysis on the relationship of variables related to mean BW.

Variables	Estimate	SE	t value	Pr (> |t|)	VIF	Adjusted R2
Intercept	6.32	30.76	0.21	< 0.001	-	0.794
Preterm births, %	−0.08	0.01	−5.91	< 0.001	0.57
LBWIs, %	−0.07	0.01	−6.43	< 0.001	0.37
Multiple births, %	0.01	0.02	0.68	0.498	0.98
Average maternal age, yr	−0.08	0.01	−5.59	< 0.001	0.64

BW = birth weight, SE = standard error, LBWIs = low birth weight infants, VIF = variance inflation factors.