Table 1.

Summary of group characteristics

Characteristic	Control n=20	IDM n=20	Assessment of Group Differences
	Mean (SD)	Mean (SD)	Note: df corrected for violation of equality of variance assumption
Age at test (months)	42.65 (5.78)	42.10 (5.75)	ns
Gestational age (weeks)	38.75 (2.05)	38.05 (2.04)	ns
Apgar scores (5 minute)	8 (1)	8 (1)	ns
Birthweight (g)	3528.60 (56.99)	3720.15 (807.89)	ns
Birthweight z-scores	0.63 (.88)	1.54 (.97)	t(26.02) = 1.86, p = .07
Birthweight z-scores > 2	1/20 or 5%	10/20 or 50%	χ2 (1, N = 40) = 10.16, p =.001
Ferritin from cord serum at birth (μg/L)	134.81 (56.99)	97.00 (75.10)	t(33.93) = 1.72, p =.095
Ferritin < 76 μg/L	2/16 or 12.5%	9/20 or 45%	χ2 (1, N = 36) = 4.43, p <.05
Full-Scale IQ WPPSI-R	112 (13)	100 (13)	t(33.68) = 2.87, p <.01
Verbal IQ	108 (13)	98 (10)	t(34.42) = 2.84, p <.01
Perceptual IQ	112 (11)	102 (16)	t(28.63) = 2.30, p <.05

WPPSI-R = Wechsler Preschool and Primary Intelligence Scale-Revised

ns = not significant