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    Introducing a new series on maternal mortality

    With death rates rising, ob/gyns must dedicate themselves to protecting each mother.


    Definitions, Risk Factors, Etiologies

    Any discussion of maternal mortality must commence with its definition. The World Health Organization (WHO) characterizes maternal mortality as death of a woman occurring while pregnant or within 42 days of termination of pregnancy regardless of the length or location of that pregnancy due to a direct or pregnancy-aggravated cause. Late maternal deaths extend beyond 42 days up to 1 year beyond the index pregnancy.3 In the United States, the Centers for Disease Control and Prevention (CDC) reports MMR through the Pregnancy Mortality Surveillance System (PMSS) identifying pregnancy-related deaths during and up to 365 days postpartum. The PMSS acquires MMR through review of maternal death certificates linked to fetal death and birth certificates. It designates maternal mortality as those maternal deaths that are the result of a “pregnancy complication, a chain of events initiated by pregnancy, or the aggravation of an unrelated condition by the physiologic effects of pregnancy.”4 Pregnancy-associated deaths identified as maternal deaths during pregnancy or within 1 year of the end of pregnancy from a cause that is unrelated to pregnancy are excluded from the MMR.  While these categorical distinctions are robust, they may underestimate maternal deaths from such important etiologies as suicide or intimate partner violence.5,6 As part of our special series, we plan to explore the nuances of case definitions and ascertainment of cases of maternal death in a dedicated article.

    Now that we have defined maternal mortality, we can examine risk modifiers. Geography appears to significantly impact the rate of maternal mortality and may be a surrogate for variable timing in implementation of the death certificate pregnancy question, disparate funding of state-wide healthcare systems, and heterogeneous population demographics.  For example, the MMR was 35.8 in 2014 in Texas, the highest of any state, compared to 15.1 in California, which is the only state to report a declining MMR.2 Examination of MMR by race and ethnicity uncovers considerable disparities. Creanga et al. reported that non-Hispanic black women had a 3.4-fold increased MMR compared to non-Hispanic white women based on 2011-2013 pregnancy-related mortality data.7 Age is also a significant risk factor with MMR increasing for all women with age peaking in those mothers age 40 or older. This has particular relevance since the percentage of pregnant women aged 35 or older compared to all women continues to increase.8 Race and age synergistically increase maternal mortality among black women aged 40 and older who have the highest risk of maternal death with an MMR of 191.6 according to the 2011-2013 PMSS data. Pre-pregnancy maternal weight also significantly influences maternal mortality. Lisonkova et al. reported that both extremes (underweight versus overweight) of body mass index (BMI) negatively impacted maternal morbidity and mortality.9 However, those with class 3 obesity corresponding (BMI ≥ 40) had an absolute risk adjusted rate difference per 10,000 women of 61.1 (95% CI, 44.8-78.9) deaths compared to pregnant women with normal BMI. While the absolute risk may be small, mothers with multiple risk factors have a compounded danger leading to a logarithmic increased threat of maternal mortality.

    What are the specific etiologies of maternal mortality? In 2017, the CDC reported that cardiovascular disease including cardiomyopathy accounted for the highest proportion of the causes of maternal mortality (26.5%,) followed by: other medical non-cardiovascular disease (14.5%), infection/sepsis (12.7%), hemorrhage (11.4%), thrombotic pulmonary embolism (9.2%), hypertensive disorders of pregnancy (7.4%), cerebrovascular accident (6.6%), amniotic fluid embolism (5.5%) and anesthesia complications (0.2%).7 Identification of cardiovascular disease as the leading cause of maternal death in the United States is surprising. It is, therefore, appropriate that Contemporary OB/GYN begins its special series on maternal mortality with this topic. Data released from the 2017 CDC Maternal Mortality Review Information Application (MARIA platform) also recognize maternal cardiovascular disease as the major etiology leading to pregnancy-related death.4 These data also reveal that the majority of maternal deaths (44.4%) occur during the first 6 weeks after pregnancy, highlighting that delivery of the fetus does not signify the end of maternal risk for morbidity and mortality.

    NEXT: Prevention

    Carolyn Zelop, MD
    Dr. Zelop is Director of Ultrasound, Fetal Echocardiography and Perinatal Research at Valley Hospital in Ridgewood, New Jersey, and ...


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