The Association Between Severity of Anemia During Pregnancy and Severe Maternal Outcomes: A Retrospective Cohort Study

Purpose: Anemia is a worldwide common condition during pregnancy, conferring a number of health risks to mothers. However, very little is known about the association between severity of anemia and severe maternal outcomes. This study aimed to assess the association between severity of anemia during pregnancy and the risk of severe maternal outcomes. Patients and Methods: This retrospective cohort study was based on data from China's National Maternal Near Miss Surveillance System for the period 2017-2018, which included 18 hospitals in southern China. Pregnant women admitted for delivery were divided into 4 groups based on severity of anemia during pregnancy: no anemia, mild anemia, moderate anemia, and severe anemia groups. Severe maternal outcomes were a composite of life-threatening conditions (ie, organ dysfunction) as defined by the WHO criteria, occurring at any time after admission until discharge or death. Modified Poisson regression analyses and propensity score-weighted regression analyses were used to estimate the relative risks (RRs) and 95% confidence intervals (CIs) of severe maternal outcomes among women with anemia of varying severity during pregnancy. Results: The incidence of severe maternal outcomes was 0.3% (417/138,556) in total, and the rates were 0.1% (85/99,755), 0.2% (30/ 18,502), 1.2% (234/19,697) and 11.3% (68/602) in no anemia, mild anemia, moderate anemia and severe anemia group, respectively. Compared with no anemia, the adjusted RR for severe maternal outcomes was 4.19 (95% CI, 3.20-5.50) in moderate anemia group and 22.12 (95% CI, 15.43-31.69) in severe anemia group; the weighted RR was 1.01 (95% CI, 1.01-1.01) in moderate anemia group and 1.11 (95% CI, 1.07-1.14) in severe anemia group. Conclusion: Moderate to severe anemia during pregnancy was independently associated with an increased risk of severe maternal outcomes. Maternal health care providers and pregnant women themselves should give more attention to the prevention and treatment of anemia during pregnancy, especially moderate to severe anemia.