Table 2 Unadjusted and multivariate-adjusted linear regression models of the associations between maternal SF and Hb levels (continuous, tertiles) and children’s T-score of CPRS-R:S subscales at age 7 years.

From: Maternal iron status during pregnancy and attention deficit/hyperactivity disorder symptoms in 7-year-old children: a prospective cohort study

	T-score of CPRS-R:S subscales
	Oppositional		Cognitive Problems/Inattention		Hyperactivity		ADHD Index
	β (95% CI)	p value	β (95% CI)	p value	β (95% CI)	p value	β (95% CI)	p value
SF levels (µg/L) at 1st period of gestation (n = 1204)*
Log-SF (per SD, continuous), unadjusted model	0.15 (− 0.41, 0.70)	0.60	0.63 (0.06, 1.19)	0.029	0.37 (− 0.21, 0.95)	0.21	0.72 (0.20, 1.24)	0.007
Log-SF (per SD, continuous), multivariate-adjusted model†	0.33 (− 0.24, 0.91)	0.25	0.47 (− 0.11, 1.05)	0.11	0.26 (− 0.34, 0.85)	0.40	0.50 (− 0.04, 1.04)	0.08
	R² = 0.043, adj.R² = 0.026, F (19, 1081) = 2.56, p < 0.001		R² = 0.076, adj.R² = 0.060, F (19, 1081) = 4.70, p < 0.001		R² = 0.077, adj.R² = 0.061, F (19, 1081) = 4.74, p < 0.001		R² = 0.079, adj.R² = 0.063, F (19, 1081) = 4.90, p < 0.001
T1 (< 21.5 μg/L)	0 (Ref.)		0 (Ref.)		0 (Ref.)		0 (Ref.)
T2 (21.5–38 μg/L)	0.51 (− 0.86, 1.88)	0.46	0.21 (− 1.17, 1.59)	0.77	0.94 (− 0.47, 2.35)	0.19	0.29 (− 1.00, 1.57)	0.66
T3 (≥ 38 μg/L)	0.18 (− 1.20, 1.57)	0.79	0.40 (− 1.00, 1.83)	0.57	− 0.09 (− 1.51, 1.33)	0.90	0.46 (− 0.84, 1.76)	0.49
p for trend^€	0.89		0.58		0.69		0.50
	R² = 0.042, adj.R² = 0.025, F (20, 1080) = 2.39, p < 0.001		R² = 0.074, adj.R² = 0.057, F (20, 1080) = 4.34, p < 0.001		R² = 0.078, adj.R² = 0.061, F (20, 1080) = 4.60, p < 0.001		R² = 0.077, adj.R² = 0.060, F (20, 1080) = 4.50, p < 0.001
SF levels (µg/L) at 1st trimester (n = 633)
Log-SF ((per SD, continuous), multivariate-adjusted model†	− 0.11 (− 0.94, 0.71)	0.79	0.46 (− 0.38, 1.30)	0.28	− 0.08 (− 0.99, 0.84)	0.86	0.54 (− 0.24, 1.32)	0.17
	R² = 0.053, adj.R² = 0.021, F (19, 565) = 1.67, p = 0.037		R² = 0.121, adj.R² = 0.09, F (19, 565) = 4–09, p < 0.001		R² = 0.079, adj.R² = 0.050, F (19, 565) = 2.57, p < 0.001		R² = 0.011, adj.R² = 0.080, F (19, 565) = 3.67, p < 0.001
T1 (< 24.2 μg/L)	0 (Ref.)		0 (Ref.)		0 (Ref.)		0 (Ref.)
T2 (24.2–41 μg/L)	0.20 (− 1.70, 2.09)	0.84	0.24 (− 1.67, 2.16)	0.80	1.23 (− 0.85, 3.31)	0.35	0.97 (− 0.81, 2.745	0.29
T3 (≥ 41 μg/L)	− 0.84 (− 2.74, 1.05)	0.38	0.28 (− 1.63, 2.19)	0.77	− 1.31 (− 3.39, 0.77)	0.21	0.45 (− 1.33, 2.23)	0.62
p for trend^€	0.32		0.79		0.12		0.75
	R² = 0.055, adj.R² = 0.022, F (20, 564) = 1.65, p = 0.037		R² = 0.121, adj.R² = 0.09, F (20, 564) = 3.82, p < 0.001		R² = 0.090, adj.R² = 0.056, F (20, 564) = 2.57, p < 0.001		R² = 0.011, adj.R² = 0.077, F (20, 564) = 3.44, p < 0.001
SF levels (µg/L) at 2nd trimester (n = 571)
Log-SF (per SD), multivariate-adjusted model†	0.57 (− 0.26, 1.40)	0.17	0.50 (− 0.33, 1.32)	0.23	0.50 (− 0.27, 1.28)	0.20	0.43 (− 0.33, 1.20)	0.26
	R² = 0.056, adj.R² = 0.020, F (19, 496) = 1.54, p = 0.066		R² = 0.066, adj.R² = 0.030, F (19, 496) = 1.83, p = 0.017		R² = 0.077, adj.R² = 0.042, F (19, 496) = 2.18, p = 0.003		R² = 0.067, adj.R² = 0.031, F (19, 496) = 1.83, p = 0.014
T1 (< 19.3 μg/L)	0 (Ref.)		0 (Ref.)		0 (Ref.)		0 (Ref.)
T2 (19.3–35.7 μg/L)	0.20 (− 1.83, 2.22)	0.85	0.90 (− 1.11, 2.91)	0.38	0.84 (− 1.04, 2.73)	0.38	0.24 (− 1.62, 2.11)	0.80
T3 (≥ 35.7 μg/L)	0.95 (− 1.12, 3.03)	0.37	1.32 (− 0.74, 3.38)	0.21	1.56 (− 0.38, 3.49)	0.11	1.13 (− 0.79, 3.04)	0.25
p for trend^€	0.34		0.24		0.12		0.23
	R² = 0.054, adj.R² = 0.016, F (20, 495) = 1.41, p = 0.109		R² = 0.066, adj.R² = 0.028, F (20, 495) = 1.75, p = 0.023		R² = 0.078, adj.R² = 0.041, F (20, 495) = 2.11, p = 0.003		R² = 0.068, adj.R² = 0.030, F (20, 495) = 1.79, p = 0.019
Hb (g/dL) at 1st trimester (n = 1101)
Hb (g/dL, continuous), unadjusted model	− 0.34 (− 0.99, 0.32)	0.31	− 0.14 (− 0.81, 0.54)	0.69	− 0.24 (− 0.92, 0.45)	0.50	− 0.05 (− 0.67, 0.57)	0.87
Hb (g/dL, continuous), multivariate-adjusted model†	− 0.24 (− 0.89, 0.41)	0.48	− 0.16 (− 0.82, 0.50)	0.63	− 0.29 (− 0.96, 0.38)	0.39	− 0.07 (− 0.68, 0.54)	0.83
	R² = 0.043, adj.R² = 0.027, F (19, 1081) = 2.58, p < 0.001		R² = 0.076, adj.R² = 0.060, F (19, 1081) = 4.72, p < 0.001		R² = 0.080, adj.R² = 0.061, F (19, 1081) = 4.71, p < 0.001		R² = 0.080, adj.R² = 0.064, F (19, 1081) = 4.96, p < 0.001
T1 (< 12.5 g/dL)	0 (Ref.)		0 (Ref.)		0 (Ref.)		0 (Ref.)
T2 (12.5–13.3 g/dL)	− 0.73 (− 2.08, 0.61)	0.28	− 1.21 (− 2.56, 0.15)	0.08	− 1.13 (− 2.52, 0.26)	0.11	− 0.85 (− 2.11, 0.41)	0.19
T3 (≥ 13.3 g/dL)	− 0.49 (− 1.86, 0.88)	0.48	− 0.09 (− 1.47, 1.29)	0.90	− 0.24 (− 1.65, 1.17)	0.74	0.10 (− 1.18, 1.38)	0.88
p for trend^€	0.48		0.90		0.72		0.86
	R² = 0.044, adj.R² = 0.026, F (20, 1080) = 2.49, p < 0.001		R² = 0.080, adj.R² = 0.063, F (20, 1081) = 4.689, p < 0.001		R² = 0.078, adj.R² = 0.061, F (20, 1081) = 4.59, p < 0.001		R² = 0.082, adj.R² = 0.066, F (20, 1081) = 4.86, p < 0.001
Hb (g/dL) at 3rd trimester (n = 1129)
Hb (g/dL, continuous), unadjusted model	− 0.01 (− 0.62, 0.60)	0.96	− 0.30 (− 0.92, 0.32)	0.34	− 0.31 (− 0.95, 0.33)	0.34	− 0.27 (− 0.85, 0.30)	0.35
Hb (g/dL, continuous), multivariate-adjusted model†	− 0.06 (− 0.66, 0.55)	0.86	− 0.26 (− 0.86, 0.35)	0.40	− 0.29 (− 0.92, 0.33)	0.35	− 0.25 (− 0.81, 0.32)	0.39
	R² = 0.041, adj.R² = 0.025, F (19, 1109) = 2.50, p < 0.001		R² = 0.077, adj.R² = 0.061, F (19, 1109) = 4.88, p < 0.001		R² = 0.073, adj.R² = 0.058, F (19, 1109) = 4.62, p < 0.001		R² = 0.078, adj.R² = 0.062, F (19, 1109) = 4.91, p < 0.001
T1 (< 11.1 g/dL)	0 (Ref.)		0 (Ref.)		0 (Ref.)		0 (Ref.)
T2 (11.1–12 g/dL)	− 0.52 (− 1.86, 0.83)	0.45	− 0.34 (− 1.69, 1.01)	0.62	− 0.42 (− 1.81, 0.97)	0.55	− 0.21 (− 1.47, 1.04)	0.74
T3 (≥ 12 g/dL)	0.18 (− 1.16, 1.53)	0.79	− 0.10 (− 1.44, 1.25)	0.89	− 0.33 (− 1.72, 1.06)	0.64	− 0.18 (− 1.43, 1.08)	0.78
p for trend^€	0.82		0.88		0.63		0.78
	R² = 0.042, adj.R² = 0.025, F (20, 1108) = 2.43, p < 0.001		R² = 0.077, adj.R² = 0.060, F (20, 1108) = 4.61, p < 0.001		R² = 0.073, adj.R² = 0.056, F (20, 1108) = 4.36, p < 0.001		R² = 0.077, adj.R² = 0.060, F (20, 1108) = 4.63, p < 0.001

CI confidence interval, SD standard deviation, BMI body mass index, T tertile, SF serum ferritin, Hb haemoglobin, CPRS-R:S Conners’ Parent Rating Scale-Revised Short Form, ADHD attention deficit hyperactivity disorder.
Linear regression models were used to calculate β coefficient (β) and 95% confidence intervals (CIs). Bold values denote a significant statistical test at a level of statistical significance p-value < 0.05. †Models were adjusted for cohorts (Gipuzkoa, Sabadell, Valencia), maternal age (years), maternal pre-pregnancy BMI (kg/m²), social class (low, medium, high), smoking during pregnancy (yes, no), mode of delivery (eutocic, dystocic), parity (primiparous, multiparous) breastfeeding (months), total iron intake above the RDA (27 mg/d) (yes, no), children’s sex (male, female), age at delivery (weeks), birth weight (kg), birth head circumference (cm), children’s age at time of test (years) and BMI-for-age z-score at age 7 years, log-SF levels in 1st period (μg/L) (for Hb analyses) and Hb levels (for SF analyses). ^€Tests for trend were conducted using the median values for each tertile of SF or Hb as a continuous variable in the multivariate regression models. *SF measurements at first and second trimester as a whole were defined as first period of pregnancy.

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Table 2 Unadjusted and multivariate-adjusted linear regression models of the associations between maternal SF and Hb levels (continuous, tertiles) and children’s T-score of CPRS-R:S subscales at age 7 years.

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