Comparisons of Severe Maternal Morbidity and Other Adverse Pregnancy Outcomes in Pregnant People With Sickle Cell Disease vs Anemia

IMPORTANCE: Pregnancy in sickle cell disease (SCD) is high risk, but whether prenatal anemia, which is treatable with red blood cell transfusions, is a mediator associated with adverse pregnancy outcomes (APOs) is not known. OBJECTIVE: To compare rates and odds of severe maternal morbidity (SMM) and other APOs in pregnancies among individuals with SCD vs those without SCD but with prenatal anemia. DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional study was conducted using data from 2012 to 2018 from the National Inpatient Sample, a nationally representative sample of 20% of acute hospital admissions in the United States. All admissions with codes for delivery of a pregnancy among people aged 11 to 55 years were included. Only admissions coded with Black race were included. Data were analyzed from September 2021 through August 2022. EXPOSURES: Prenatal anemia and SCD. MAIN OUTCOMES AND MEASURES: SMM was tabulated per the Center for Disease Control and Prevention SMM Index alongside other APOs. Multiple logistic regression was used to compare the odds for APOs and risk ratios (RRs) to compare rates of APOs. RESULTS: Among 764 455 total delivery admissions among patients identified as Black (mean [SD] age at delivery, 27.00 [6.08] years), 3200 deliveries were coded with maternal SCD, 34 808 deliveries were coded with maternal anemia, and 726 447 deliveries were control. Most patients were publicly insured (499 060 [65.4%]). For most outcomes, including SMM and mortality per 10 000 deliveries, the SCD group had higher rates (SMM: 5.9%; 95% CI, 5.1%-6.8%; maternal mortality: 13.0 deaths; 95% CI, 4.9 to 35.0 deaths) than anemia (SMM: 2.1%; 95% CI, 2.0%-2.3%; maternal mortality: 0.9 deaths; 95% CI, 0.3 to 2.8 deaths) or control groups (SMM: 1.1%; 95% CI, 1.0%-1.1%; maternal mortality: 1.2 deaths; 95% CI, 1.0 to 1.5 deaths). SCD (adjusted odds ratio [aOR], 5.51; 95% CI, 4.71-6.45) and anemia groups (aOR, 2.00; 95% CI, 1.84-2.17) had higher adjusted odds of SMM compared with the control group. However, for many complications associated with ischemia or abnormal placentation, CIs of aORs for SCD and anemia groups overlapped (eg, eclampsia: aOR, 2.74; 95% CI, 1.51-4.96 vs aOR, 1.40; 95% CI, 1.08-1.81). For these complications, RRs for SCD vs anemia were between 1.0 and 2.1 (eg, eclampsia: 1.76; 95% CI, 0.93-3.32). For complications associated with thrombosis or SCD-specific pathologies, rates and aORs were greater for the SCD vs anemia group. For these complications, RRs were between 3.70 and 10.90. For example, rates of acute respiratory distress syndrome, including acute chest syndrome, were 56 of 3144 deliveries (1.8%) vs 122 of 34 686 deliveries (0.4%), and the RR was 4.99 (95% CI, 3.65-6.84). CONCLUSIONS AND RELEVANCE: This study found that risks associated with prenatal anemia and SCD were similar for many APOs, especially those associated with ischemia and abnormal placentation, suggesting that prenatal anemia may be a mediator associated with pregnancy risk in individuals with SCD.