Table 1. Proportion of children under exclusive and predominant breastfeeding and the underlying prevalence ratios and confidence intervals according to characteristics of the children and their mothers. Ribeirao Preto, SP, Southeastern Brazil, 2011.

Variable	n	EB (%)	PR	95%CI	p	PB (%)	PR	95%CI	p
Age group of child					< 0.001 ^a				0.093 ^a
< 1 month	123	62.2	1			8.5	1
1 \|– 2 months	135	45.5	0.73	0.58;0.92		14.4	1.70	0.78;3.68
2 \|– 3 months	152	38.1	0.61	0.48;0.79		17.7	2.08	0.99;4.34
3 \|– 4 months	185	28.7	0.46	0.35;0.60		25.6	3.01	1.51;5.99
4 \|– 5 months	161	23.6	0.38	0.28;0.52		12.6	1.49	0.67;3.29
5 \|– 6 months	160	11.5	0.18	0.12;0.29		16.2	1.91	0.85;4.30
Sex					0.358				0.108
Male	474	31.8	1			14.0	1
Female	442	34.7	1.09	0.91;1.31		18.6	1.33	0.94;1.39
Birth weight					0.158				0.326
< 2,500 g	78	26.0	1			11.9	1
≥ 2,500 g	817	34.1	1.32	0.90;1.95		16.8	1.40	0.71;2.76
Type of delivery					0.992
Cesarean	540	33.2	1			12.2	1		0.001
Vaginal	376	33.2	1.00	0.91;1.10		22.5	1.84	1.31;2.61
Maternal age group
< 20 years	103	22.6	1		0.044 ^a	34.8	1		0.002 ^a
20 \|– 35 years	188	37.3	1.65	1.14;2.40		14.6	0.42	0.28;0.62
≥ 35 years	105	35.3	1.57	1.00;2.44		13.3	0.38	0.20;0.72
Maternal parity					0.001				0.701
Primiparous	415	29.6	1			17.3	1
Multiparous	398	40.9	1.38	1.14;1.68		16.2	0.93	0.65;1.34
Employment status					< 0.001 ^a				0.536^a
Working outside the home	163	23.5	1			15.5	1
Not working outside the home	415	35.5	1.52	1.12;2.06		18.9	1.22	0.74;2.01
On maternity leave	234	42.5	1.81	1.32;2.49		13.4	0.90	0.51;1.59
Education					0.106 ^a				0.001 ^a
≤ 8 years of study	189	32.0	1			25.4	1
9 \|– 12 years of study	444	34.5	1.08	0.84;1.38		16.6	0.65	0.44;0.96
≥ 12 years of study	181	40.2	1.26	0.95;1.66		9.7	0.38	0.21;0.68

EB: exclusive breastfeeding; PB: predominant breastfeeding

^a p of linear trend.

Values of p < 0.20 are presented in bold.