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.