Abstract
Objective Non-Hispanic Black people (NHBP) have a three-fold higher rate of maternal mortality
compared to other racial groups. Racial disparities in maternal morbidity are well-described;
however, there are substantial differences in cultural, economic, and social determinants
of health among racial groups. We thus sought to study the at-risk, non-Hispanic Black
population as its own cohort to identify factors most associated with severe maternal
morbidity (SMM).
Study Design This is a population-based retrospective case–control study of all live births in
the United States between 2017 and 2019 using birth records obtained from the National
Center for Health Statistics. The primary outcome for this study was to determine
demographic, social, medical, and obstetric factors associated with maternal morbidity
among NHBP who did and did not experience an SMM event. Multivariable logistic regression
was used to estimate the adjusted odds ratio between each individual factor and the
outcome of SMM among NHBP.
Results Of the 1,624,744 NHBP who delivered between 2017 and 2019, 1.1% experienced an SMM
event defined as a composite of blood product transfusion, eclamptic seizure, intensive
care unit admission, unplanned hysterectomy, and uterine rupture. The rates of these
individual SMM events per 10,000 deliveries were 50, 40, 20, 5, and 4 among NHBP,
respectively. Among NHBP, factors associated in multivariable regression analysis
with SMM in order of strength of association included cesarean delivery, earlier gestational
age at delivery, preeclampsia, induction of labor, chronic hypertension, prior preterm
birth, lower educational attainment, multifetal gestation, advanced maternal age,
pregestational diabetes, and cigarette smoking. The population attributable fraction
for cesarean delivery, preterm birth, and pregnancy-induced hypertensive disease for
the outcome of SMM were 0.46, 0.23, and 0.07, respectively.
Conclusion The three factors most associated with SMM among NHBP are potentially avoidable or
modifiable by aggressive screening, prevention, and treatment of preeclampsia and
preterm birth as well as reducing cesarean rates in this population.
Key Points
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The rate of SMM in NHBP may be modifiable.
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NHBP have a three-fold higher rate of maternal mortality.
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Preeclampsia, preterm birth, and cesarean sections are most associated with maternal
morbidity.
Keywords
severe maternal morbidity - preeclampsia - preterm birth - black pregnancy outcomes
