Summary of findings 2. Miscarriage (defined as delivery before 24 weeks of gestation).

Patient or population: women with threatened miscarriage or a history of recurrent miscarriage Interventions: multiple progestogens (vaginal micronized progesterone, oral micronized progesterone, dydrogesterone and 17‐α‐hydroxyprogesterone) Comparison: placebo and dydrogesterone Outcome: miscarriage (defined as delivery before 24 weeks of gestation) Settings: hospitals
Treatment	Direct evidence		Indirect evidence		Anticipated absolute effects for direct estimate
	RR (95% CI)	Certainty	RR (95% CI)	Certainty	Risk with intervention	Risk with comparator	Risk difference with intervention
Threatened miscarriage
Vaginal micronized progesterone versus placebo	0.90 [0.80, 1.01]	⊕⊕⊕⊕ HIGH	Unavailable	‐	201 per 1000 (vaginal micronized progesterone)	224 per 1000 (placebo)	22 fewer per 1000 (from 45 fewer to 2 more)
Dydrogesterone versus placebo	0.90 [0.55, 1.47]	⊕⊕⊕⊝ MODERATEa	Unavailable	‐	129 per 1000 (dydrogesterone)	143 per 1000 (placebo)	14 fewer per 1000 (from 64 fewer to 67 more)
17‐α‐hydroxyprogesterone versus placebo	Not reported by included studies	‐	Unavailable	‐	See comment*	See comment**	See comment***
Oral micronized progesterone versus dydrogesterone	0.67 [0.25, 1.75]	⊕⊝⊝⊝ VERY LOWb	Unavailable	‐	102 per 1000 (oral micronized progesterone)	153 per 1000 (placebo)	50 fewer per 1000 (from 114 fewer to 114 more)
Oral micronized progesterone versus placebo	Unavailable	‐	0.74 [0.25, 2.17]	⊕⊝⊝⊝ VERY LOWc	See comment*	See comment**	See comment***
Vaginal micronized progesterone versus dydrogesterone	Unavailable	‐	1.00 [0.60, 1.66]	⊕⊕⊕⊝ MODERATEd	See comment*	See comment**	See comment***
Vaginal micronized progesterone versus oral micronized progesterone	Unavailable	‐	1.22 [0.41, 3.62]	⊕⊝⊝⊝ VERY LOWc	See comment*	See comment**	See comment***
Recurrent miscarriage
Vaginal micronized progesterone versus placebo	0.96 [0.79, 1.17]	⊕⊕⊕⊕ HIGH	Unavailable	‐	321 per 1000 (vaginal micronized progesterone)	334 per 1000 (placebo)	13 fewer per 1000 (from 70 fewer to 57 more)
Dydrogesterone versus placebo	1.00 [0.23, 4.37]	⊕⊝⊝⊝ VERY LOWe	Unavailable	‐	150 per 1000 (dydrogesterone)	150 per 1000 (placebo)	0 fewer per 1000 (from 115 fewer to 505 more)
17‐α‐hydroxyprogesterone versus placebo	0.85 [0.28, 2.58]	⊕⊝⊝⊝ VERY LOWe	Unavailable	‐	185 per 1000 (17‐α‐hydroxyprogesterone)	217 per 1000 (placebo)	33 fewer per 1000 (from 157 fewer to 343 more)
Oral micronized progesterone versus dydrogesterone	Unavailable	‐	Unavailable	‐	See comment*	See comment**	See comment***
Vaginal micronized progesterone versus dydrogesterone	Unavailable	‐	0.96 [0.22, 4.24]	⊕⊝⊝⊝ VERY LOWf	See comment*	See comment**	See comment***
Dydrogesterone versus 17‐α‐hydroxyprogesterone	Unavailable	‐	1.18 [0.19, 7.44]	⊕⊝⊝⊝ VERY LOWf	See comment*	See comment**	See comment***
Vaginal micronized progesterone versus 17‐α‐hydroxyprogesterone	Unavailable	‐	1.13 [0.37, 3.49]	⊕⊝⊝⊝ VERY LOWf	See comment*	See comment**	See comment***
*No included studies or there are no events in included studies to estimate the baseline risk. **Absolute risk with intervention cannot be estimated in the absence of absolute risk with the comparator. ***Risk difference cannot be estimated in the absence of absolute risks with intervention and the comparator. CI: Confidence interval; RR: Risk ratio.
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.

^a Direct evidence downgraded ‐1 due to serious limitations in study design.

^b Direct evidence downgraded ‐1 due to serious limitations in study design (unclear allocation concealment) and ‐2 due to and severe imprecision (wide 95% CIs and small number of events).

^c Indirect evidence downgraded ‐1 due to serious limitations in study design (unclear allocation concealment) and ‐2 due to and severe imprecision (wide 95% CIs and small number of events).

^d Indirect evidence downgraded ‐1 due to serious limitations in study design.

^e Direct evidence downgraded ‐1 due to serious limitations in study design (unclear random sequence generation and allocation concealment) and ‐2 due to and severe imprecision (wide 95% CIs and small number of events).

^f Indirect evidence downgraded ‐1 due to serious limitations in study design (unclear random sequence generation and allocation concealment) and ‐2 due to and severe imprecision (wide 95% CIs and small number of events).