Relation between spontaneous or induced abortion and development of breast cancer*
| Risk factor | Relative 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 abortion | 0.98 (0.92 to 1.04) |
| Induced abortion | 0.93 (0.89 to 0.96) |