Abstract: The search retrieved 62 reports in total. Of these, we assessed 12 reports in full, corresponding to six trials. We included three trials and excluded one; two trials are ongoing. The included trials were conducted in hospital settings. Two trials were conducted in India; the third trial was a large cluster-randomised trial, which took place in 13 European countries. Overall, we judged the included trials to be at a low risk of bias. One study evaluated the use of calibrated drapes versus visual estimation, another evaluated the use of calibrated drapes versus the gravimetric technique (weight of blood-soaked materials), therefore, we were unable to pool the data from the two studies. The third study did not measure any of the outcomes of interest, so did not contribute data to the analyses. Direct measurement using calibrated drapes versus visual estimation One cluster-randomised controlled trial in 13 western European countries, with over 25,000 women, examined this comparison. The trial did not report on postpartum anaemia (defined as Hb lower than 9 mg/dL), blood loss greater than 500 mL, or maternal infection. Moderate-quality evidence suggests there is probably little or no difference between groups in: severe morbidity (coagulopathy, organ failure, intensive care unit admission; adjusted risk ratio (RR) 0.82, 95% confidence interval (CI) 0.48 to 1.39); the risk of blood transfusion (adjusted RR 0.82, 95% CI 0.46 to 1.46); the use of plasma expanders (adjusted RR 0.77, 95% CI 0.42 to 1.42); and the use of therapeutic uterotonics (adjusted RR 0.87, 95% CI 0.42 to 1.76). Direct measurement using calibrated drapes (Excellent BRASSS-V Drape™) versus gravimetric technique One randomised controlled trial in India, with 900 women, examined this comparison. The trial did not report on postpartum anaemia (defined as Hb lower than 9 mg/dL), severe morbidity, or maternal infection. High-quality evidence showed that using calibrated drapes improved the detection of blood loss greater than 500 mL when compared with the gravimetric technique (RR 1.86, 95% CI 1.11 to 3.11). Low-quality evidence suggests there may be little or no difference in the risk of blood transfusion between the two groups (RR 1.00, 95% CI 0.06 to 15.94), or in the use of plasma expanders, reported as intravenous fluids given for PPH treatment (RR 0.67; 95% CI 0.19 to 2.35). High-quality evidence showed little or no difference in the use of therapeutic uterotonics (RR 1.01, 95% CI 0.90 to 1.13), but the use of therapeutic uterotonics was extremely high in both arms of the study (57% and 56%). Overall, the evidence in this review is insufficient to support the use of one method over another for blood loss estimation after vaginal birth. In general, the quality of evidence for our predefined outcomes ranged from low to high quality, with downgrading decisions due to imprecision. The included trials did not report on many of our primary and secondary outcomes. In trials that evaluate methods for estimating blood loss during vaginal birth, we believe it is important to measure their impact on clinical maternal and neonatal outcomes, along with their diagnostic accuracy. This body of knowledge needs further, well designed, appropriately powered, randomised controlled trials that correlate blood loss with relevant clinical outcomes, such as those listed in this review.

Plain-language summary: We searched for evidence in February 2018, and found three randomised controlled trials, involving over 26,000 women. Two trials contributed data to our analyses; one study did not provide data for any of the outcomes of interest in this review. All of the trials took place in hospital settings. Two trials took place in India, the other was conducted in 13 different European countries. The trials examined different methods of estimating blood loss. One trial (conducted in 13 European countries, involving over 25,000 women) compared the use of a calibrated drape (direct estimation) to visual estimation (indirect estimation). Moderate-quality evidence showed there was probably little or no difference between the methods for the risk of women developing serious conditions (e.g. failure to form clots, poor functioning of the liver, kidneys, and brain, admission to intensive care); their need for blood transfusion; the use of fluids to maintain their blood pressure; or the use of drugs to help their uterus contract to stop the bleeding. The trial did not report the number of women who had anaemia after birth, blood loss of at least 500 mL, or infection. One trial (conducted in India, involving 900 women) compared the use of a calibrated drape (direct estimation) to weighing and measuring blood and blood-soaked materials (indirect method). High-quality evidence showed that calibrated drapes were better than measuring the blood and blood-soaked materials at detecting blood loss of at least 500 mL. Low-quality evidence showed there may be little or no difference between methods in the need for blood transfusion or fluids to maintain blood pressure. High-quality evidence showed little or no difference in the use of drugs to help the uterus contract in order to stop bleeding. The trial did not report the number of women who had anaemia after birth or infection, or the risk of developing serious conditions (such as failure to form clots, poor functioning of the liver, kidneys, and brain, or being admitted to intensive care). There was insufficient evidence to support the use of one method over another to estimate blood loss after vaginal birth. There is a need for high quality trials that measure important outcomes, such as those listed in this review.