Summary of findings for the main comparison. Direct estimation using calibrated drapes compared to indirect estimation using visual estimation for blood loss estimation after vaginal birth.

Direct estimation using calibrated drapes compared to indirect estimation using visual estimation for estimating blood loss after vaginal birth
Patient or population: women undergoing vaginal birth Setting: 78 maternity units from 13 European countries Intervention: direct estimation using calibrated drapes Comparison: indirect estimation using visual estimation
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	№ of participants (studies)	Quality of the evidence (GRADE)	Comments
	Risk with visual estimation	Risk with using calibrated drapes
Postpartum anaemia	trial did not report outcome		‐	‐	‐
Severe morbidity	Study population		Adjusted RR 0.82 (0.48 to 1.39)	2999 (1 RCT)	⊕⊕⊕⊝ Moderate a	The actual numbers of severe PPH were 189/11,037 vaginal deliveries in the calibrated drapes group, and 295/14,344 vaginal deliveries in the visual estimation group.
	21 per 1000	17 per 1000 (10 to 29)
Blood loss ≥ 500 mL	trial did not report outcome		‐	‐	‐
Blood transfusion	Study population		Adjusted RR 0.82 (0.46 to 1.46)	5561 (1 RCT)	⊕⊕⊕⊝ Moderate a
	10 per 1000	8 per 1000 (4 to 14)
Use of plasma expanders	Study population		Adjusted RR 0.77 (0.42 to 1.42)	3122 (1 RCT)	⊕⊕⊕⊝ Moderate a
	15 per 1000	12 per 1000 (6 to 22)
Use of therapeutic uterotonics	Study population		Adjusted RR 0.87 (0.42 to 1.76)	593 (1 RCT)	⊕⊕⊕⊝ Moderate a
	54 per 1000	47 per 1000 (23 to 95)
Maternal infection	trial did not report outcome		‐	‐	‐
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; RR: risk ratio; PPH: postpartum haemorrhage
GRADE Working Group grades of evidence High quality: we are very confident that the true effect lies close to that of the estimate of the effect Moderate quality: 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 quality: our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low quality: we have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

^a Imprecision: wide confidence interval crossing the line of no effect