輸血
The greatest proportion of women with SMM are those who require a blood transfusion during delivery, mostly due to excessive bleeding. Blood transfusions given during delivery due to excessive bleeding has increased the rate of mothers with SMM. The rate of SMM has increased almost 200% between 1993 (49.5 per 100,000 live births) and 2014 (144.0 per 100,000 live births). This can be seen with the increased rate of blood transfusions given during delivery, which increased from 1993 (24.5 per 100,000 live births) to 2014 (122.3 per 100,000 live births).