Recurrence of Postpartum Hemorrhage—the Swedish Medical Birth Register
Abstract Number: BP-6
Abstract Type: Original Research
Introduction: Postpartum hemorrhage (PPH) is a major cause of maternal morbidity and the incidence of PPH has been increasing in developed countries. While a history of PPH is a recognized risk factor for PPH in subsequent pregnancies, little is known about how the risk accumulates after multiple affected pregnancies, how this is modulated by the severity of prior PPHs, and how recurrence risk varies by PPH subtype. We report risks of PPH according to women’s PPH history in the Swedish population.
Methods: The cohort consisted of 538,244 primiparous women included in the Medical Birth Register between 1997-2009. PPH was defined using diagnostic codes based on >1 liter of estimated blood loss. It was further classified as severe if the parturient received a blood transfusion. We estimated relative risks (RR) and 95% confidence intervals (CI) for PPH comparing women with and without a history of PPH.
Results: Risk of PPH was 5.5% in first pregnancies, and 4% in later pregnancies. Compared to women without any previous PPH, women with PPH in their first pregnancy had a greatly increased risk of PPH in subsequent pregnancies (Figure 1). PPH risk was 12.9 % in the second pregnancy among women with PPH in their first pregnancy compared to 3.8% among women without PPH in their first pregnancy (RR 3.3; CI 3.2-3.5). In women with severe PPH in their first pregnancy, this RR was 4.2 (CI: 3.9-4.6). For third pregnancies, the risk was 24.2% when both prior pregnancies were affected, compared to 3.4% among women without PPH in their first two pregnancies (RR 7.2; CI: 5.9-8.8).
Similar patterns of recurrence risk were observed in subanalyses of PPH due to uterine atony and PPH due to other causes. Excluding women with stable risk factors for PPH expected to be present across all pregnancies (including coagulopathy, fibroids, diabetes) did not substantially change patterns of recurrence, nor did accounting for mode of delivery.
Conclusions: PPH risk is highest among women with >1 consecutive affected deliveries and in those with a previous severe PPH. These women should be delivered in hospitals with the anesthesia, obstetric, and blood bank resources to readily respond to a PPH; the care team should anticipate an increased likelihood of bleeding. The presence of recurrence risk across all PPH subtypes may point to a sub-clinical coagulopathy as the mechanism of recurrent PPH.