INTRODUCTION
The goal of defining a blood loss threshold that defines a significant
obstetrical hemorrhage (OBH) is to find a sensitive and specific
quantity of obstetrical bleeding that should trigger closer monitoring
or interventions to prevent perinatal morbidity and
mortality.1 Historical definitions of obstetric
hemorrhage have primarily been based in expert-opinion rather than
evidence-based thresholds of morbidity or mortality.2
The first proposed definition of postpartum hemorrhage traces back to a
report published after an informal meeting of experts in 1989 at the
World Health Organization, which defined PPH as “greater than 500mL
blood loss from the genital tract after the delivery of a baby” but
also acknowledged this as an “arbitrary figure” and “not always of
great clinical significance.”2,3 In 2014, as part of
the “reVITALize” initiative, the American College of Obstetricians and
Gynecologists (ACOG) established a new definition of OBH as 1,000cc of
cumulative blood loss regardless of route of delivery or specific vital
sign changes associated with blood loss.4 This
initiative focused on decreasing morbidity and mortality by
standardizing the obstetrical definitions and approaches utilized by
providers in the United States in the care of birthing people in labor.
However, while a small cohort of historical data from Pritchard et al.,
which followed peripartum patients using 51 chromium labeled red cells,
demonstrated mean losses to be around 500mL in vaginal deliveries and
around 1000mL in cesarean deliveries, there is little contemporary data
that demonstrates a specific association between obstetric blood loss of
1,000cc and clinically significant adverse perinatal
outcomes.5
To address this “arbitrary” definition of OBH, we investigate the
cumulative quantitative blood loss (QBL) associated with increased risk
of severe obstetric hemorrhage-related morbidity (OBH-M). We also seek
to compare the predictiveness for OBH-M of the current definition of OBH
to an alternate definition derived from our cohort.