The clinical benefit of blood transfusion: a hypothetical experiment based on a nationwide survey of severe maternal morbidity

Background: It is beyond doubt that blood transfusion services have added to the decline in maternal mortality in high-resource countries. To quantify the clinical benefit of red blood cell (RBC) transfusion in obstetric care, we performed a hypothetical experimental study using data from a prospective nationwide cohort of women giving birth in the Netherlands.

Study design and methods: Data were abstracted from a nationwide cohort study on severe maternal morbidity, including obstetric haemorrhage requiring 4 or more units of RBC, to obtain an observed and a hypothetical control group consisting of the same women. In the hypothetical control group, we simulated a situation where RBC transfusion was unavailable and estimated how many of these women would have died in that situation. A questionnaire survey asked experts in major (obstetric) haemorrhage to choose a critical minimal number of RBC transfusions at which a woman with obstetric haemorrhage would have died if RBC transfusion was not available. Maternal mortality rate per 100,000 maternities [maternal mortality ratios (MMR)] and relative risk were calculated for the observed and hypothetical group.

Results: The observed MMR was 13 per 100,000 maternities. According to 47 responding experts, the median number of RBC units without which a woman would have most probably died was nine, resulting in a hypothetical MMR of 87 per 100,000 maternities (relative risk 6·5; 95% confidence interval 4·2-10·0).

Conclusions: It can be expected that unavailability of RBC transfusion in obstetric care increases the risk of maternal death 6.5-fold. Blood transfusion thus largely contributes to the decline of MMR and would also be an important pillar of improving quality of care in resource-poor settings.