The association between the degree of social vulnerability and maternal anemia and other adverse perinatal outcomes.

Objective: Maternal anemia in pregnancy is associated with many adverse maternal, fetal, and neonatal outcomes. The role of social determinants of health (SDOH) in the development of maternal anemia and other adverse outcomes is continually evolving. One such newer tool, the Social Vulnerability Index (SVI), measures an individual's community-level SDOH, with higher SVI denoting higher vulnerability. Our objective was to evaluate the association between SVI, maternal anemia, and other adverse perinatal outcomes. Methods: Retrospective cohort study of pregnant individuals delivering singletons at a gestational age ≥23 weeks at a single center from 2014 to 2018. Patients with sickle cell disease, on anticoagulation, or with a PO Box, missing address, or residential address that could not be geocoded, were excluded. SVI scores were assigned to each patient based on their geographic home address and categorized into SVI tertiles: low (SVI 0-0.33), moderate (0.33-0.66), and high vulnerability (0.67-1.00). The primary outcome was anemia per ACOG guidelines (hemoglobin or hematocrit less than 11 g/dL and 33% in the first trimester, respectively, 10.5 g/dL and 32% in the second trimester, respectively, and 11 g/dL and 33% in the third trimester, respectively). Secondary outcomes included select labor outcomes, a composite of postpartum maternal morbidity, and a composite of neonatal morbidity. Multivariable logistic regression models estimated the association between moderate and high SVI and outcomes, compared to low SVI. The mean overall SVI score and SVI theme scores were compared for patients with and without anemia; individual SVI theme components were also analyzed. A mediation analysis using bootstrapping evaluated the contribution of anemia to the other adverse perinatal outcomes associated with SVI. Results: Of 13,951 individuals, 3989 (29%) lived in a low SVI area, 3976 (29%) lived in a moderate SVI area, and 5986 (43%) lived in a high SVI area. Patient characteristics varied significantly based on the SVI, as high SVI areas had patients who were younger, non-Latinx Black, single, publicly insured, and more likely to have greater body mass index (BMI), chronic hypertension, and substance use issues; moderate SVI areas had more Latinx patients with diabetes; and low SVI areas had patients who were older, nulliparous, married, and privately insured. Compared to patients with low SVI, those with greater vulnerability had significantly higher odds of anemia (moderate SVI: aOR, 1.11 [1.00-1.24]; high SVI: aOR, 1.18 [1.05-1.32]). Preeclampsia, composite postpartum maternal morbidity, and neonatal morbidity also increased with increasing vulnerability. Patients with anemia had higher mean SVI scores overall and across the four SVI themes. In mediation analysis, 36% of the association between SVI and maternal morbidity was significantly mediated by anemia ( Conclusion: Patients living in moderate and high areas of social vulnerability are more likely to have anemia and other adverse perinatal outcomes. While some increase in the perinatal morbidity associated with increasing SVI is mediated through anemia, other factors and social determinants of health are likely also contributory.