Am J Obstet Gynecol MFM . Associations of influenza, chronic comorbid conditions, and severe maternal morbidity among U.S. pregnant women with influenza at delivery hospitalization, 2000-2015

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Am J Obstet Gynecol MFM


. 2021 Jul 22;100445.
doi: 10.1016/j.ajogmf.2021.100445. Online ahead of print.
Associations of influenza, chronic comorbid conditions, and severe maternal morbidity among U.S. pregnant women with influenza at delivery hospitalization, 2000-2015


Brittany Arditi ¹ , Timothy Wen ² , Laura E Riley ³ , Mary D'Alton ¹ , Nasim C Sobhani ² , Alexander M Friedman ¹ , Kartik K Venkatesh ⁴



Affiliations

• PMID: 34303850
• DOI: 10.1016/j.ajogmf.2021.100445

Abstract

Background: Chronic comorbid conditions increase the risk of influenza-related morbidity. Whether this holds for pregnant women who are at high risk of complications from influenza remains to be determined.
Objectives: To determine whether chronic comorbid conditions are associated with an increased risk of severe maternal morbidity (SMM) among pregnant women with an influenza diagnosis at delivery hospitalization.
Study design: We performed a cross-sectional analysis of delivery hospitalizations complicated by an influenza diagnosis using the National Inpatient Sample from 2000-2015. We assessed four prevalent chronic comorbid conditions associated with increased influenza-complications outside of pregnancy, obstructive lung disease (asthma and chronic obstructive pulmonary disease [COPD]), chronic hypertension, obesity, and pregestational diabetes, overall and individually. The primary outcome was SMM excluding transfusion as defined by the Centers for Disease Control and Prevention, and secondarily, specific SMM measures recognized as influenza-related complications, acute respiratory distress syndrome (ARDS), mechanical intubation and ventilation, and sepsis and shock. Multivariable survey-weighted log linear models were used, adjusting for patient, hospital, and clinical characteristics.
Results: Of 62.7 million delivery hospitalizations, 0.2% (n=144,572) were complicated by an influenza diagnosis at delivery hospitalization (23 cases of influenza per 10,000 delivery hospitalizations), and 24.9% (n=36,054) with 1 or more chronic comorbid conditions, of which 77.4% included obstructive lung disease. Pregnant women with an influenza diagnosis at delivery hospitalization with a chronic comorbid condition had a slightly higher risk of SMM compared to those without (2.6% vs. 1.7%; adjusted risk ratio (aRR): 1.11; 95% CI: 1.03, 1.21), as well as ARDS (0.9% vs. 0.5%; aRR: 1.42; 95% CI: 1.23, 1.64) and mechanical intubation and ventilation (0.2% vs. 0.1%; aRR: 1.92; 95% CI: 1.37, 2.69), but a lower risk of sepsis and shock (0.2% vs. 0.3%; aRR: 0.57; 95% CI: 0.45, 0.73). Regarding specific conditions, obstructive lung disease was associated with an increased risk of SMM (adjusted risk ratio (aRR): 1.21; 95% CI: 1.11, 1.32), as well as ARDS (aRR: 1.54; 95% CI: 1.32, 1.79) and mechanical intubation and ventilation (aRR: 2.80; 95% CI: 2.00, 3.91). Chronic hypertension was associated with an increased risk of ARDS (aRR: 1.70; 95% CI: 1.16, 2.49), but a lower risk of sepsis and shock (aRR: 0.34; 95% CI: 0.13, 0.85). Obesity was associated with a lower risk of SMM (aRR: 0.84; 95% CI: 0.74, 0.97). Pregestational diabetes was not associated with SMM.
Conclusions: Among women with a diagnosis of influenza at delivery hospitalization, chronic comorbid conditions may increase the risk of SMM, and in particular, those outcomes related to influenza. These results can inform efforts to increase influenza vaccination for pregnant women with chronic comorbidities.

Keywords: chronic comorbidity; flu; influenza; pregnancy; severe maternal morbidity.