Relation between spontaneous or induced abortion and development of breast cancer*

Risk factorRelative risk of breast cancer (95% CI)†
*Abbreviations defined in glossary.
†Relative risk of breast cancer associated with ⩾1 pregnancy ending as an abortion compared with never having had such a pregnancy. Relative risk <1 indicates a reduced risk of breast cancer. Analyses stratified by parity and age at first birth.
Spontaneous abortion0.98 (0.92 to 1.04)
Induced abortion0.93 (0.89 to 0.96)