There was no significant difference in the occurrence of breast
cancer between women who had and had not had children
(OR¼ 0.9, 95% CI 0.5–1.7 for ever versus never having children), nor
was there a significant relation with number of births or the age
awomanwas when her first childwas born (OR¼ 1.0, 95% CI 0.3–3.1
for those aged 30 or more at first birth versus those aged 25 or less).
A similar result was seen for breastfeeding (of the youngest child)
amongst parous women (OR¼ 0.8, 95% CI 0.2–3.1). The number of
case women with only one birth, and thus complete breastfeeding
information, was too small (n ¼ 5) to examine the effects in this
group alone.