Population-based study of risk factors for severe maternal morbidity.
BACKGROUND
Severe maternal morbidity (SMM) is a serious health condition potentially resulting in death without immediate medical attention, including organ failure, obstetric shock and eclampsia. SMM affects 20000 US women every year; however, few population-based studies have examined SMM risk factors.


METHODS
We conducted a population-based case-control study linking birth certificate and hospital discharge data from Washington State (1987-2008), identifying 9485 women with an antepartum, intrapartum or postpartum SMM with ≥3-day hospitalisation or transfer from another facility and 41 112 random controls. Maternal age, race, smoking during pregnancy, parity, pre-existing medical condition, multiple birth, prior caesarean delivery, and body mass index were assessed as risk factors with logistic regression to estimate odds ratios (OR) and 95% confidence intervals [CI], adjusted for education and delivery payer source.


RESULTS
Older women (35-39: OR 1.65 [CI 1.52, 1.79]; 40+: OR 2.48 [CI 2.16, 2.81]), non-White women (Black: OR 1.82 [CI 1.64, 2.01]; American Indian: OR 1.52 [CI 1.32, 1.73]; Asian/Pacific Islander: OR 1.30 [CI 1.19, 1.41]; Hispanic: OR 1.17 [CI 1.07, 1.27]) and women at parity extremes (nulliparous: OR 1.83 [CI 1.72, 1.95]; parity 3+: OR 1.34 [CI 1.23, 1.45]) were at greater risk of SMM. Women with a pre-existing medical condition (OR 2.10 [CI 1.88, 2.33]), a multiple birth (OR 2.54 [CI 2.26, 2.82]) and a prior caesarean delivery (OR 2.08 [CI 1.93, 2.23]) were also at increased risk.


CONCLUSIONS
The risk factors identified are not modifiable at the individual level; therefore, provider and system-level factors may be the most appropriate target for preventing SMM.
Department of Epidemiology, University of Washington School of Public Health, Department of Obstetrics and Gynecology, University of Washington School of Medicine, Fred Hutchinson Cancer Research Institute, Seattle, WA 98195-7236, USA. kpietila@uw.edu
Kristen E
KE
Gray
Erin R
ER
Wallace
Kailey R
KR
Nelson
Susan D
SD
Reed
Melissa A
MA
Schiff
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008423:Maternal Age; D063130:Maternal Death / Q000706:statistics & numerical data*; D008875:Middle Aged; D009017:Morbidity; D016017:Odds Ratio; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D012307:Risk Factors; D012959:Socioeconomic Factors; D014861:Washington / Q000453:epidemiology; D055815:Young Adult