Procedures and outcomes
anaemia, bleeding, tachycardia, fatigue, shock, blood loss, breathlessness
ANAEMIA, BLEEDING, SHOCK, BLOOD LOSS, HAEMODYNAMIC INSTABILITY, SHOCKED, POSTPARTUM HAEMORRHAGE
The exposure was prebirth haemoglobin concentration and the outcome was postpartum haemorrhage defined in one of three ways: (1) clinical postpartum haemorrhage, (2) WHO-defined postpartum haemorrhage, and (3) calculated postpartum haemorrhage. Firstly, clinical postpartum haemorrhage is diagnosed by a clinician usually because the patient has an estimated blood loss of at least 500 mL, or any blood loss sufficient to compromise haemodynamic stability within 24 h of the birth. Clinicians at each site were trained to estimate blood loss by the lead obstetrician and the trial team. We used pictorial guides, with photographs of soiled pads and bed sheets, to aid visual estimation of blood loss. Haemodynamic instability was based on signs such as low blood pressure, tachycardia, or reduced urine output. Secondly, we used the 1989 WHO working group definition for WHO-defined postpartum haemorrhage measurements, which is blood loss of at 500 mL or more from the genital tract within 24 h of a vaginal birth.Because anaemia reduces the oxygen-carrying capacity of blood, women with anaemia cannot tolerate the same volume of bleeding as healthy women and become shocked after a smaller blood loss. Given the lack of an established definition of postpartum haemorrhage in women with anaemia, before conducting this study, we examined different definitions of postpartum haemorrhage in terms of their specificity for substantial bleeding (defined as shock index ≥1·0) and their association with fatigue, physical endurance, and breathlessness.