Time of cycle | 1st day of menstruation ± 5 days | 1st day of menstruation ± 2 days | ||||||
---|---|---|---|---|---|---|---|---|

Relative risk | 95% CI | Significance | No. of women^{*} | Relative risk | 95% CI | Significance | No. of women | |

Premenstruation is the 5 (or 2) days before menstruation; menstruation is the 1st day of bleeding and the subsequent 5 (or 2) days. | ||||||||

* The number of women on whom the relative risk is based. | ||||||||

† “All other times” is defined as the days of the cycle other than day 1 of menstruation ± 5 days. | ||||||||

Premenstruation | 1.25 | 1.10–1.42 | p < 0.001 | 150 | 1.71 | 1.45–2.01 | p < 0.0001 | 150 |

Menstruation | 2.19 | 2.01–2.40 | p < 0.0001 | 155 | 2.50 | 2.24–2.77 | p < 0.0001 | 154 |

All other times^{†} | 1.00 | — | — | — | 1.00 | — | — | — |