Table 2.

Results from a mixed-effects linear regression model. Estimation error (square root of absolute value) is the outcome. A random effect for resident is included. Parameter estimates (B), 95% confidence intervals, and p-values are included. A piecewise linear spline was used for the overall model, while a natural cubic spline was used for the stratified models.

	Overall Model			Stratified Models
				Full-Term: Leopold’s			Full-Term: Ultrasound			Preterm: Ultrasound
Predictors	B	CI	p	B	CI	p	B	CI	p	B	CI	p
BMI (10-unit increase)	0.08	0.03 – 0.12	0.001	0.10	0.02 – 0.17	0.01	0.11	0.03 – 0.18	0.006	0.03	−0.05 – 0.10	0.529
Estimation (Ultrasound vs. Leopold’s)	−0.87	−1.48 – -0.26	0.005
Birthweight (100g) (<1600g)	0.85	0.62 – 1.08	<0.001
Birthweight (100g) (1600–3800g)	−0.07	−0.13 – −0.01	<0.001
Birthweight (100g) (>3800g)	0.96	0.69 – 1.23	<0.001
Birthweight: Spline 1				−97.71	−117.66 – -77.77	<0.001	−6.27	−12.38 – -0.15	0.045	11.95	8.08 – 15.82	<0.001
Birthweight: Spline 2				−5.38	−8.99 – -1.77	0.003	6.18	2.29 – 10.08	0.002	4.7	1.38 – 8.02	0.006
N (residents)	33 id			33 id			33 id			33 id
N (observations)	1697			651			639			407