(420) Adverse perinatal outcomes associated with anemia in early and late pregnancy

Anemia in early pregnancy may lead to adverse perinatal outcomes, but evidence is limited. Further, it is unknown if resolution of anemia during pregnancy mitigates the risk. We evaluated perinatal outcomes of those with anemia in the first trimester and of those with resolved and persistent anemia by late pregnancy, compared with those without anemia in the first trimester.


Study Design:

We used the Merative™ Marketscan® Commercial Database of nationwide insurance claims data during 2018-2023. We identified anemia with trimester-specific thresholds for hemoglobin (Hgb) and hematocrit (Hct). We classified anemia as resolved if ≥1 normal Hg/Hct value in late pregnancy (≥24 weeks’ gestation) and as persistent otherwise. We defined perinatal outcomes using diagnosis and procedure codes. We used inverse probability of treatment weights and modified Poisson regression to estimate associations between anemia and anemia resolution with perinatal outcomes.

Results:

Among 73,586 pregnancies, 4.4% had anemia in the first trimester. Of those with ≥1 Hgb/Hct value in late pregnancy (72.1%), 53.4% had persistent and 46.6% had resolved anemia. Compared with those without anemia in the first trimester, those with anemia, regardless of resolution, had at least twofold higher risk of blood products transfusion and severe postpartum hemorrhage and 46% higher risk of non-transfusion severe maternal morbidity (ntSMM) (adjusted risk ratio [aRR] 2.45, 95% confidence interval [CI]: 1.91, 3.13; aRR 1.99, 95% CI: 1.39, 2.85; and aRR 1.46, 95% CI: 1.13, 1.89) (Figure 1). Risk of ntSMM was increased among those with persistent anemia (aRR 1.64, 95% CI: 1.13, 2.37), but not among those with resolved anemia (aRR 1.07, 95% CI: 0.65, 1.74) (Figure 2). Risk of other outcomes was similar for those with persistent and resolved anemia.


Conclusion:

Findings suggest that anemia in the first trimester increases risk of adverse perinatal outcomes, and resolution of anemia by late pregnancy reduces but does not eliminate risk. This research emphasizes the clinical importance of anemia in early pregnancy and the need for adequate treatment.