Outcomes* | Anticipated absolute effects† (95% CI) | Relative effect (95% CI) | Number of participants (studies) | Certainty of the evidence (GRADE) | |
Risk with no contraception | Risk with any type of hormonal contraception (oestrogen plus progestin or progestin-only) | ||||
Hospitalisation | 38 per 1000 |
38 per 1000
(26 to 54) |
OR 0.99
(0.68 to 1.44) | 123 (1 observational study) | ⊕⊝⊝⊝ Very low‡§¶ |
Intubation | 0 of 79 patients who did not use hormonal contraception required intubation compared with 0 of 44 patients who used hormonal contraception. | 123 (1 observational study) | ⊕⊝⊝⊝ Very low‡§¶ |
GRADE Working Group grades of evidence
High certainty: we are very confident that the true effect lies close to that of the estimate of the effect.
Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.
Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect.
Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.
*The outcomes of mortality, VTE, arterial thromboembolism, and ARDS were not measured and are not included in this table.
†The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
‡Downgraded for serious risk of bias given no ascertainment of hormonal contraception exposure and no information on variables used for adjustment, increasing risk of residual confounding.
§Downgraded for indirectness as the study was not performed in patients confirmed to be using contraception at time of outcome.
¶Downgraded 2 levels for imprecision due to small sample size with wide CI with results reported in only 1 study.
ARDS, acute respiratory distress syndrome; VTE, venous thromboembolism.