Table 1. Characteristics of study participants included in these analyses by parity and breastfeeding.

Population characteristics	By parity					By breastfeedinga		All women
	Nulliparous	One	Two	Three	Four or more	Never breastfed	Ever breastfed
	n=89 448	n=100 639	n=309 841	n=159 100	n=80 600	n=201 688	n=449 492	n=740 628
Age in years (mean (s.d.))	57 (5)	57 (5)	57 (4)	58 (4)	58 (4)	57 (4)	58 (4)	58 (4)
Parity (mean (s.d.))	0	1 (0)	2 (0)	3 (0)	4.4 (0.8)	2.1 (0.9)	2.5 (1.0)	2.1 (1.2)
Number of children breastfed (mean (s.d.))	0	0.5 (0.5)	1.1 (0.9)	1.7 (1.2)	2.5 (1.8)	0	1.9 (1.0)	1.2 (1.2)
Women who ever breastfed (%)	0	52	68	76	80	0	100	70
Duration breastfeeding
Total duration in months (mean (s.d.))	0	1.9 (3.5)	4.3 (6.2)	6.8 (8.7)	10.5 (13.9)	0	7.7 (8.8)	4.7 (7.8)
Duration per child in months (mean (s.d.))	0	1.9 (3.5)	2.1 (2.9)	2.3 (2.9)	2.3 (3.0)	0	3.1 (3.1)	1.9 (2.9)
In lower third of socioeconomic group (%)	33	34	30	36	51	39	33	34
Current smokers (%)	17	20	17	19	25	23	17	19
Strenuous physical activity less than once a week (%)	26	30	27	28	34	34	26	28

^aAmong parous women.