Table 1.

Baseline Sociodemographic Characteristics and Parity of Parous Women (n=100 864) in the 45 and Up Study by Breastfeeding History and Average Breastfeeding Duration Per Child^a

Variables	Breastfeeding History			Average Breastfeeding Duration Per Childb
	Never Breastfed	Ever Breastfed	P Valuec	>0 to 6 Months	>6 to 12 Months	>12 Months	P Valued
No. of subjects, %	12 517 (12.4)	88 347 (87.6)		56 049 (63.4)	24 549 (27.8)	7749 (8.8)
Age group, %
45 to 54 y	26.5	37.7	<0.0001	29.5	47.3	66.9	<0.0001
55 to 64 y	42.7	34.0		36.5	29.7	28.9
≥65 y	30.8	28.3		34.0	23.0	4.2
Mean (SD) age for first child, y	24.3 (5.15)	25.1 (4.89)	<0.0001	24.3 (4.66)	26.0 (4.74)	28.1 (5.29)	<0.0001
Mean (SD) age for last child, y	28.9 (5.24)	30.6 (4.96)	<0.0001	29.8 (4.93)	31.6 (4.64)	33.4 (4.7)	<0.0001
Parity
Mean (SD) parity (no. of births)	2.4 (1.13)	2.7 (1.18)	<0.0001	2.8 (1.2)	2.8 (1.15)	2.6 (1.13)	<0.0001
1 child, %	19.0	8.7	<0.0001	16.7	9.5	3.9	<0.0001
2 children, %	43.7	39.8		47.7	46.4	41.5
3 children, %	23.8	31.2		24.3	29.8	35.0
≥4 children, %	13.5	20.3		11.3	14.3	19.6
Country of birth, %
Australia	72.0	77.3	<0.0001	74.0	76.1	79.7	<0.0001
Other	28.0	22.7		26.0	23.9	20.3
Highest education, %e
University and higher	11.1	23.8	<0.0001	16.3	21.3	27.0	<0.0001
High school/trade apprenticeship/certificate/diploma	33.3	38.4		37.1	37.9	39.4
≤10 y	55.6	37.8		46.6	40.8	33.6
Marital status, %f
Married/living with a partner	72.7	75.8	<0.0001	74.6	75.0	76.7	<0.0001
Single/divorced/separated/widowed	27.3	24.2		25.4	25.0	23.3
Socioeconomic status (SEIFA‐IRSD), %g
Quintile 1 (most disadvantaged)	23.2	19.7	<0.0001	21.1	19.8	18.2	<0.0001
Quintile 2	20.3	19.5		20.1	18.8	19.0
Quintile 3	22.5	21.4		21.8	21.2	20.7
Quintile 4	19.0	19.6		19.7	19.6	20.0
Quintile 5 (least disadvantaged)	15.0	19.8		17.3	20.5	22.0

SEIFA‐IRSD indicates Socio‐Economic Indexes For Area—Index of Relative Socio‐Economic Disadvantage.

^aData are presented as means (SD) or percentages.

^bAverage breastfeeding duration per child was calculated as self‐reported lifetime breastfeeding duration divided by the reported number of children.

^cBased on chi‐square test for categorical variables and Student t test for continuous variables.

^dBased on chi‐square test for categorical variables and F statistics from ANOVA for continuous variables.

^e1325 missing.

^f268 missing.

^g66 missing.