Determining the incidence of postpartum haemorrhage among Ontario women with and without inherited bleeding disorders: a population-based cohort study

Introduction — At a population level, there is a poor understanding of the incidence and pre-disposing risk factors of postpartum haemorrhage (PPH) among women with inherited bleeding disorders (IBD).

Aim — To determine the incidence of PPH, and identify maternal factors associated with risk of PPH among women with IBD.

Methods — We conducted a retrospective cohort study using data housed within ICES (formerly known as the Institute for Clinical Evaluative Sciences). The cohort included women with an in-hospital, live or stillborn delivery, between January 2014 and December 2019. The primary outcome was PPH (identified by ICD-10 code O72). PPH incidence and risk factors were compared between women with and without IBD. Temporal trends were assessed using the Cochrane-Armitage test. Between group differences were assessed using standardised differences (std. difference).

Results — Total 601,773 women were included; 2002 (.33%) had an IBD diagnosis. PPH incidence was 1.5 times higher (7.3 vs. 4.9 cases/100 deliveries, std. difference .1) among women with IBD compared to women without. Women with IBD were slightly older (31.7 vs. 30.7 years), had higher rates of hypertension, previous PPH, and induction of labour. Women with IBD were more frequently diagnosed with anaemia (4.8% vs. 1.8%; std difference .17) and had lower haemoglobin levels at admission for delivery compared to women without IBD.

Conclusions — This study contributes to the literature regarding obstetric bleeding among women with IBD, showing that anaemia at delivery may be an important risk factor for PPH. Given their predisposition to anaemia, clarifying this relationship will optimise management and outcomes.