INTRODUCTIONImmediate postpartum haemorrhage (PPH) is defined as blood loss ≥ 500 mL after normal vaginal delivery.(1-3) This obstetric complication is a leading cause of maternal death worldwide. To prevent the occurrence of PPH, current evidence supports active management of the third stage of labour, especially the prescription of oxytocin, as standard obstetric care.(1-3) However, the optimal method for determining the volume of postpartum blood loss for early detection of PPH remains unclear.Although the ideal measurement of postpartum blood loss involves the use of objective tools, visual estimation is still commonly used in daily obstetric practice.(4) Photospectometry is the gold standard blood loss measurement technique due to its accuracy. However, this technique is complicated, costly and impractical. Additionally, photospectrometry cannot be applied at all levels of healthcare and is more suitable for clinical research.(4,5) In a previous study, an alternative method weighed soaked swabs or drapes after delivery, which proved to be effective for the early detection of PPH.(6) However, this method substantially increases the workload of medical staff members and may not be suitable in a busy hospital setting.The use of sterile under-buttock or postpartum drapes is another method of postpartum blood loss measurement. This method is suitable for low-resource hospitals, as it is inexpensive, convenient and easy to use. Previous studies have shown that it produced results that highly correlated with those of standard photospectrometry (correlation coefficient [r] = 0.93), with a reduction in postpartum haemoglobin levels reported. (5,7,8) Therefore, this method was chosen as the gold standard in the present study.The purpose of this study was to compare the efficacy of visual estimation and objective measurement using the sterile under-buttock drape to determine the volume of postpartum blood loss in PPH. We hope that the results of this study will lead to improvements in standard obstetric care for the early detection of immediate PPH. METHODSWith the ethical approval of the Siriraj Institutional Review Board, the present study was prospectively conducted from June 2013 to December 2013. Pregnant Thai women aged ≥ 18 years who were admitted in the early phase of labour were included in the study. Women who had painful contractions, were near delivery, or were under the sedative effect of morphine or its derivatives were excluded. This study also excluded women who had bleeding disorders (e.g. idiopathic thrombocytopenic purpura), dependence on bleeding-related medication (e.g. aspirin), a Caesarean delivery, fetal anomalies or a stillbirth. All the