Risk of recurrent red‐cell transfusion in delivery: A nationwide longitudinal study

Objective To investigate the risk of recurrent maternal red‐cell transfusion in delivery. Design Nationwide long‐standing retrospective cohort study. Setting Swedish medical birth register. Population All registered births from 2000 to 2017 in Sweden. Methods We included all women with between one and three consecutive registered births from 22 weeks of gestation onwards and all maternal red‐cell transfusions in the peripartum period within the defined period of study. Information on gestational and non‐gestational comorbidity was collected and we identified any female siblings. In our analyses we compared the risk of red‐cell transfusion in delivery in relation to transfusion history and gestational and non‐gestational comorbidity. Main outcome measures Maternal peripartum red‐cell transfusion, defined as a recorded transfusion in the period from 1 day before and 7 days after delivery. Results We included 825 451 women with a total 1 419 909 deliveries, including 786 097 (55.4%) first, 511 398 (36.0%) second and 122 414 (8.6%) third deliveries. Of women with previous obestric transfusion, 8.7% were transfused in a second delivery, compared with 1.7% of women without transfusion or diagnosis of haemorrhage. A previous diagnosis of haemorrhage did not affect the odds ratio of transfusion recurrence. Among women who were transfused in their first two deliveries, 15.5% were transfused in third delivery, corresponding to an 11‐fold increase, compared with non‐transfused women (adjusted odds ratio aOR 11.5, 95% CI 7.9–16.6). Women with a sister transfused in delivery were at increased risk of transfusion in a second delivery (aOR 1.8, 95% CI 1.6–2.1). Conclusions Women with previous red‐cell transfusion are at an increased risk of red‐cell transfusion in a subsequent delivery, compared with women without a history of red‐cell transfusion.