Table 1.

Characteristics of the Study Population

	Cases Subjects		Control Subjects
	Mean ± SD		Mean ± SD		P^*
Age (years)
Mother	27.7 ± 6.7		24.5 ± 6.1		.001
Father	32.5 ± 10.0		28.5 ± 8.2		.006
	N	%	N	%	P^†
Schooling (years)
Mother
≤4	12	23.5	23	22.5	.758
5 to 11	37	72.5	77	75.5
≥12	2	3.9	2	2.0
Father^‡
≤4	8	16.7	20	20.2	.840
5 to 11	38	79.2	74	74.7
≥12	2	4.2	5	5.1
Skin colour
Mother
White	33	64.7	53	52.0	.134
Nonwhite	18	35.3	49	48.0
Father^‡
White	33	66.0	56	54.9	.192
Nonwhite	17	34.0	46	45.1
Mother and father cohabiting
Yes	39	76.5	81	79.4	.677
No	12	23.5	21	20.6
Current employment
Mother
Yes	14	27.5	20	19.6	.271
No	37	72.5	82	80.4
Father^‡
Yes	38	77.6	73	72.3	.490
No	11	22.4	28	27.7
Monthly family income (minimum wages^¶)
≤3	25	49.0	43	42.6	.691
4 to 10	23	45.1	53	52.5
>10	3	5.9	5	5.0
Household conditions
Good/average	46	90.2	93	91.2	.843
Poor	5	9.8	9	8.8
Number of children
≤3	38	74.5	92	90.2	.010
≥4	13	25.5	10	9.8
Prenatal follow-up
5 visits	44	86.3	89	87.3	.865
<5 visits	7	13.7	13	12.7
Baby’s sex
Female	22	43.1	52	51.0	.360
Male	29	56.9	50	49.0
Birthweight
≥2500 g	49	96.1	94	92.2	0.355
<2500 g	2	3.9	8	7.8
Birth order
Firstborn	14	27.5	49	48.0	.015
Other	37	72.5	53	52.0
Method of delivery
Vaginal	35	68.6	77	75.5	.366
Caesarean	16	31.4	25	24.5
Length of gestation
≥37 weeks	41	80.4	82	81.2	.906
<37 weeks	10	19.6	19	18.8
Mother-baby separation due to hospitalization of mother
No	45	88.2	99	97.1	.029
Yes	6	11.8	3	2.9
Rooming-in
Yes	33	66.0	83	83.0	.019
No	17	34.0	17	17.0
Maternal smoking
No	26	68.4	57	71.3	.753
Yes	12	31.6	23	28.8

* Student’s t test.
† χ² test.
‡ Number of fathers varies because some mothers could not give or refused to give information about non-cohabiting fathers.
¶ MW, minimum monthly wage in Brazil (about US $70).