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Recording available 2/16-5/2
Recording available 2/16-5/2
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Poster Session 4

Category: Obstetric Quality and Safety

Poster Session 4

(1103) Severe maternal morbidity associated with the individual and interactive effects of influenza, asthma, and hypertension

Thursday, February 12, 2026
3:30 PM - 5:00 PM  

    Submitting Author and Presenting Author(s)

  • HR

    Havilah Reimche-Vu, BS

    Medical Student
    Loma Linda University School of Medicine
    Loma Linda, California, United States

    • Coauthor(s)

  • BP

    Bo Park, MPH, PhD

    Associate Professor
    California State University, Fullerton
    Fullerton, California, United States

  • Nida Ali, BS (she/her/hers)

    Clinical Research Coordinator III
    Loma Linda University Children's Health | Perinatal Institute
    Loma Linda, California, United States

  • Ashra Tugung, CCRP

    Clinical Research Coordinator
    Loma Linda University Children's Health | Perinatal Institute
    Loma Linda, California, United States

  • NT

    Neville Tritch, BS

    Medical Student
    Loma Linda University School of Medicine
    Loma Linda, California, United States

  • Kriti N. Vedhanayagam, DO

    PGY-3 Resident
    Loma Linda University
    Loma Linda, California, United States

  • KH

    Kevin H. Hu, MD

    Loma Linda University
    Loma Linda, California, United States

  • Sergio A. Karageuzian, DO

    PGY-2 Resident
    Loma Linda University Health
    Loma Linda, California, United States

  • Ilish Gedestad, DO

    PGY-1 Resident
    Loma Linda University Health
    Loma Linda, California, United States

  • Ruofan H. Yao, MD, MPH

    Maternal Fetal Medicine Faculty
    Loma Linda University
    Loma Linda, California, United States

Objective:
To evaluate the association between influenza, asthma, hypertension (HTN), and their combined interaction with the risk of severe maternal morbidity (SMM).

Study Design:
This is a population-based, retrospective cohort study using the California Office of Statewide Health Planning and Development Linked Birth File with hospital discharge International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) diagnoses between 2007 and 2012. Chi-square tests were used to determine the association between influenza, asthma, HTN, and SMM. Cox proportional hazard analysis determined the risk of SMM associated with each condition, both individually and combined. A cumulative hazard graph was made to show the timing of SMM events during pregnancy due to these conditions.

Results:

Among the 3,076,580 individuals analyzed, 45,261 (1.47%) experienced SMM. Women who did not have influenza, asthma, or HTN were the majority (2,980,400; 98.58%), with a reference SMM rate of 1.42%.  



Individuals with influenza only (n = 576) had an elevated SMM rate of 12.15% (HR 9.24 [95% CI: 7.31-11.69]). Those with HTN only (n = 14,254) had a SMM rate of 5.62% (HR 5.43 [95% CI: 5.06-5.83]). Individuals with asthma only (n = 80,277) showed a SMM rate of 2.30% (HR 1.48 [95% CI: 1.41-1.55]).  



Comorbid conditions were associated with compounding risk. The interaction of flu and asthma (n = 49) resulted in a SMM rate of 16.33% (HR 14.17 [95% CI: 7.09-28.34]). Those with influenza and HTN (n = 7) had an elevated SMM rate of 71.43% (HR 58.17 [95% CI: 24.20-139.82]). Individuals with asthma and HTN (n = 1,016) had a SMM rate of 8.07% (HR 7.31 [95% CI: 5.89-9.08]). The influenza, asthma, and HTN (n = 1) cohort was too small to associate with SMM risk.


Conclusion:
This study shows that influenza, HTN, and asthma are all independent risk factors associated with SMM. Influenza infection had a multiplicative effect on other risk factors associated with SMM. Whereas asthma and HTN demonstrated only additive effects on SMM.