Diana S. Wolfe, Afshan B. Hameed, and Elliott Main
•The United States is one of eight countries in the world with a rising maternal mortality rate 
•Cardiovascular disease is the leading cause of indirect maternal deaths in the United States 
•Qualitative maternal mortality reviews are essential in addition to vital statistics to comprehend maternal mortality 
•Implementation of toolkits, quality improvement projects, and safety bundles have been proven to decrease maternal mortality rates in California 
•Perinatal quality collaboratives essentially bring stakeholders together to a common goal of improving maternal morbidity and mortality 
There has been a global effort to establish reliable statistics on maternal mortality. This has been a challenge due to differences in reporting systems; however, the World Health Organization (WHO), United Nations International Children’s Emergency Fund (UNICEF), United Nations Fund for Population Activities (UNFPA), World Bank Group, and the United National Population Division recently published an executive summary on mortality statistics between 1990–2015 . Their goal was in part to establish accurate and internationally comparable measures of maternal mortality to help accomplish the United Nations new millennium goal to decrease maternal mortality by 2015. Their refined measuring system allowed for comparability and a measure of uncertainty around the country-specific estimates. Globally, the maternal mortality ratio has fallen by 44%; however, the burden remains high especially for low-resource countries which accounted for 99% of global maternal deaths in 2015. Region-specific distributions are displayed in Figure 1.1 . Sub-Saharan Africa accounts for the majority load of maternal deaths at 66%.
Figure 1.1 Worldwide map of rates of maternal mortality per 100 000 live births. (From WHO, UNICEF, UNFPA, World Bank Group, and the United Nations Population Division. Trends in Maternal Mortality: 1990 to 2015. Geneva: WHO; 2015. With permission.)
A WHO systematic study on etiology of maternal mortality worldwide analyzed and combined data from the years 2003–2009 [1,6]; a total of 73% of cases were due to direct obstetric causes of death, including hemorrhage 27%, hypertensive disorders 14%, embolism 2%, sepsis 10%, abortion 9%, and other direct causes 24%, leaving approximately 27% accounted for indirect obstetric causes. Internationally, HIV/AIDS accounts for only a small proportion (1.6%) of maternal deaths.
Maternal mortality in the United States has gained recent attention because of the surprising increase in its rate, contrary to all other high-resource countries. Approximately 700 women die each year in the United States due to pregnancy or related complications . There are also stark racial and ethnic disparities with black and Native American women having rates two to four times those of white or Asian women [8,2] (Figure 1.2). This disparity in maternal mortality is the largest disparity noted for any public health metric and has led to the mobilization of multiple organizations for important local and national efforts. Maternal mortality data is produced by two branches of the Centers for Disease Control and Prevention (CDC) . The National Center for Health Statistics (NCHS) produces data to calculate the WHO definition of maternal mortality (death during or within 42 days after the termination of a pregnancy from a cause related to the pregnancy or its treatment). This determination is made by review of International Classification of Disease (ICD) codes from the death certificate alone. Death certificate causes of death are publicly available from the CDC, but there is serious concern over the quality of the data and the limitations of the 42-day boundary. For these reasons, NCHS has not released an official U.S. maternal mortality rate since 2007.
The Reproductive Health branch of the CDC established the Pregnancy Mortality Surveillance System (PMSS) in collaboration with the American College of Obstetricians and Gynecologists in 1986 to understand the causes of death and risk factors and thus provide a more comprehensive review of maternal deaths. Starting with all deaths from any cause during or within 12 months of a birth/loss (cohort of pregnancy-associated mortalities), case reviews of all data on the death certificate and more recently on linked birth certificates, is used to establish whether the death was causally related to the pregnancy or its care (pregnancy-related mortalities) [10,11]. (See Box 1.1.)
Create a multidisciplinary SMM review committee
Identify potential SMM cases and confirm true SMM
Identify the morbidity
Abstract and summarize data
Present case to review committee for discussion
Determine events leading to morbidity
Determine opportunities to improve outcomes
Assess system and patient factors for the opportunity to improve outcomes
Effect change and evaluate improvement