Maternal antepartum anaemia and its association with transfusion and perinatal outcomes: a 10-year retrospective cohort study.

Introduction: Maternal anaemia may identify women at increased risk of transfusion and adverse peripartum outcomes. We examined these associations and described selected local outcome rates prior to the implementation of a formal obstetric patient blood management (PBM) pathway. Material and methods: This retrospective cohort included singleton delivery from 25 July 2012 to 31 December 2021. Anaemia was defined as haemoglobin < 11.0 g/dl in the complete blood count. The primary outcome was red blood cell (RBC) transfusion during the index hospitalisation. Models were adjusted for maternal age, body mass index, mode of delivery, calendar year, and delivery order. Because some women contributed more than one delivery, standard errors were clustered at the woman level. Neonatal analyses were exploratory. Results: 7.1% of cases were classified as anaemic. Red blood cell transfusion occurred in 107/1,153 episodes with anaemia (9.3%) and 249/15,189 without anaemia (1.6%; adjusted odds ratio [aOR] 7.34, 95% confidence interval [CI]: 5.60-9.63). Postpartum instrumental uterine exploration occurred in 4.1% vs. 2.8%, respectively (aOR 1.94, 95% CI: 1.39-2.72). Preterm birth before 37 weeks occurred in 26.7% vs. 11.2%, respectively (aOR 2.75, 95% CI: 2.37-3.18). Low birthweight and low Apgar scores were more frequent in episodes with anaemia, but their estimates approached the null after additional adjustment for gestational age. Conclusions: Haemoglobin-defined anaemia at admission for delivery was strongly associated with RBC transfusion during the index hospitalisation. These data provide a partial local pre-implementation baseline for future prospective evaluation but do not establish anaemia aetiology, treatment effectiveness, or a causal benefit of PBM.