In which region would you expect to find the highest maternal mortality ratio

Global Maternal Mortality

Globally in 2015, an estimated 303,000 women died while pregnant or within 42 days of the end of pregnancy.1 This number corresponds to a ratio of 216 maternal deaths per 100,000 live births and to a 1-in-180 lifetime risk for pregnancy-related death for each girl entering her childbearing years (Table 39.1).1 According to the World Health Organization (WHO), “No issue is more central to global well-being than maternal and perinatal health. Every individual, every family and every community is at some point intimately involved in pregnancy and the success of childbirth.”2

Definitions for maternal death are listed inTable 39.2, and measures of maternal mortality are listed inTable 39.3. More than 99% of maternal deaths occur in low- and middle-income countries, with 84% in either sub-Saharan Africa or South Asia (Fig. 39.1). Between 1990 and 2015,1 the globalmaternal mortality ratio (MMR) fell by 44%, an impressive improvement, but less than the 75% reduction targeted by the Millennium Development Goals. In 2015, the United Nations issued 17 Sustainable Development Goals, including a commitment to reduce the global MMR to less than 70 per 100,000 live births by 2030, with no single country having an MMR of more than 140. Several regions will require substantial investment to meet this goal, most notably sub-Saharan Africa, where the lifetime risk for maternal death remains remarkably high, at 1 in 36.1 There is considerable regional variation. Within sub-Saharan Africa, the highest MMRs are in Sierra Leone (1360), Central African Republic (882), and Chad (856) and represent rates that are 10-fold higher than the lowest ratios in the region.1 Throughout the world, war, natural disaster, and political conflict can degrade health systems and trigger a rise in deaths caused by complications that would be treatable under stable conditions.1

Measures of Maternal Mortality

The maternal mortality ratio (MMR) is defined as the number of maternal deaths in a given time period divided by the number of live births (per 100 000 live births) during the same period:

MMR=NumberofmaternaldeathsNumberoflivebirths ×1/100000

MMR is considered to be high if it is greater than or equal to 300 maternal deaths per 100 000 live births and extremely high if it is greater than or equal to 1000 maternal deaths per 100 000 live births; low MMR defined as 20–99 maternal deaths per 100 000 live births, moderate MMR defined as 100–299 maternal deaths per 100 000 live births.

Although other measures of maternal mortality such as maternal mortality rate (defined as the number of maternal deaths in a population divided by the number of women of 15–49 years of age (or woman-years lived at 15–49 years of age)) and proportion of maternal deaths among deaths of women of reproductive age (defined as the number of maternal deaths in a given time period divided by the total deaths among women of 15–49 years of age) have been used in the literature, MMR is generally regarded as the preferred measure of maternal mortality because it describes the frequency of maternal death relative to its risk pool, as measured (imperfectly, but not badly) by the number of live births.

Epidemiology

It is estimated that there were 303,000 (95% confidence interval [CI], 291,000–349,000) maternal deaths worldwide in 2015.3 This is a maternal mortality ratio (MMR) of 216 per 100,000 live births (95% CI, 207–249), which is a relative decrease of 43.9% from the 385 (95% CI, 359–427) noted in 1990.3 The MMR varies considerably by region. In 2015, it was 12 per 100,000 (95% CI, 11–14) in high-income countries but was as high as 546 per 100,000 (95% CI, 511–652) in sub-Saharan Africa.3

The dramatic fall in the US MMR during the 20th century has been heralded as a success for both public health programs and obstetrics providers (Figs. 50.1 and50.2).7 The decline, from rates approximating 900 per 100,000 births in 1901 to 9 per 100,000 in 1991, occurred in other resource-rich countries also. This success has been attributed to many factors: the movement of most births to hospitals; improved hygiene and aseptic technique; common use of prenatal care, including screening for preeclampsia; the introduction of blood transfusions and antibiotics; widespread availability of obstetric anesthesia; an increase in training and expertise of obstetrics providers; and an improvement in the overall health of the population. Although all of these may be important, the period of greatest decline was in the 1930s and 1940s, when many hospital-based advances were being introduced. Although the United States in the 1930s was not resource-rich, the advent of state and city maternal mortality review committees focused attention on causes of and solutions for maternal mortality. Developing community consensus that involves collaboration between the public health system and hospitals and providers, together with forming a local maternal mortality review committee (MMRC), should be considered the model when maternal mortality and morbidity are addressed.

More recently, however, the national US metrics for maternal mortality have been rising. In 2014, the MMR in the United States was 23.8 per 100,000 live births.4,8 In large part, the increase is due to improved ascertainment. However, there also has been an increase in population risk factors such as maternal age and obesity. Even when increased ascertainment is accounted for, maternal mortality in the United States is substantially higher than in other resource-rich countries.

State and national MMRs are underestimated when using only death certificate codes compared with analyses using enhanced surveillance techniques, such as linked birth and death certificates. In the United States between 1999 and 2007, a series of changes were made to improve the accuracy of maternal mortality data. ICD-10–coded death certificates had more categories for maternal death than those coded by the Ninth Revision (ICD-9) had. A new standard death certificate was introduced in 2003 that offered a pregnancy checkbox to identify women who were pregnant at the time of death or had delivered within the prior 42 days (or, in some states, 365 days). Given the small numbers of maternal deaths, modest improvements in case ascertainment would be expected to lead to increased rates. Clinical factors that contributed to the higher risk for maternal mortality in this time interval included increases in maternal age and obesity, rises in cesarean rates, and obstetric hemorrhage. Thus it is difficult to determine the relative contributions of improved data collection and of clinical and patient factors to the increased MMRs.

B. Maternal Mortality

Maternal mortality is estimated at greater than one-half million women per year dying during childbirth (about 1,440 per day), most in underdeveloped nations (Steinberg, 1989; Wright, 1994). Of these, 1% occur in developed countries which represent about 20% of the world population. The remaining 99% is distributed within approximately 80% of the world population, representing an average 20-fold higher rate. Based on an estimated 148 million annual births, the global maternal mortality rate is 338/100,000 births versus about 10 or less in the industrialized Western societies. The goal for North America in the 1990s is a reduction to 5/100,000 births (Steinberg, 1989). High maternal mortality is directly linked to public health deficiencies, illiteracy, early marriage and multiparity, and cultural practices. An estimated 35% reduction in maternal mortality could be accomplished if women who desire no more children were able to practice family planning and avoid pregnancy in early and late reproductive ages and high parity that is associated with maternal mortality. Where high standards of living, application of family planning, and availability of good health care services exist, basic pathophysiologies of pregnancy including hemorrhage, infection, unsafe abortion, hypertension, and obstructed labor remain the leading causes of maternal mortality (World Health Statistics Annual, 1994). Less than one-half of all pregnancies around the world are delivered in an institution or with professional assistance (World Health Organization, 1992).

Maternal Health and the Burden of Death and Disability

“Many Births Mean Many Burials”

—Kenyan Proverb

Every year worldwide, it is estimated that more than 300,000 mothers die from preventable causes during pregnancy, birth, and the postnatal period—approximately 830 women every day.1,2 Despite ongoing efforts by the global health community, the death rate has dropped by only 44% overall since 1975, far less than the 75% decline anticipated after the introduction of the United Nation (UN) Millennium Development Goals (MDGs) in 1990.3 Despite recent initiatives, which in some resource-poor countries have resulted in quite significant declines over the past few years, too little has happened too late. The irrefutable fact is that the main preventive or remediable interventions to reduce maternal deaths have been well known for many years, and nearly all of these tragedies could be avoided at little or no extra cost. Lives would be saved in those countries which carry a significant burden of maternal and newborn deaths if there was stronger political will to improve the lives of women by placing women's health and reproductive rights far higher up the agenda rather than at the tail end of services, as so often happens. As the father of the Safe Motherhood movement, Professor Mahmoud Fathalla famously said“women are not dying of diseases we cannot treat…they are dying because societies have yet to decide that their lives are worth saving.”4

Maternal deaths and disabilities are eminently avoidable if women have a choice about becoming pregnant and, once pregnant, if they have access to essential health services that provide evidence-based, technologically appropriate, and affordable interventions even in the poorest countries of the world. For example, a UN report estimated that if all women who wanted to space or avoid pregnancy were able to access and use an effective modern method of contraception, the global number of unintended pregnancies would drop by 70% and the number of unsafe, potentially fatal abortions would drop by 74%. In addition, if all pregnant women and their newborn babies received only the basic standards of maternity care recommended by the World Health Organization (WHO), the number of women dying would fall by two-thirds and those of their babies would decrease by more than three-quarters.5

Deaths are merely the tip of the iceberg. Globally it is estimated that more than 300 million women are living with short- or long-term pregnancy-related complications, with approximately 20 million new cases occurring each year.6,7 In addition, these figures generally do not include the poorly recognized or accepted burden of mental health. In most countries, postnatal depression, suicide from puerperal psychosis, and other mental health issues are not even acknowledged as pregnancy-related problems, and the stories of legions of women dying or suffering from these debilitating conditions remain untold.

Maternal mortality and cardiovascular disease

Maternal mortality has been steadily increasing in the United States. Over the course of 22 years (from 1987 to 2009), for every 100,000 pregnancies, the maternal mortality increased from 7.2 to 17.8 [12]. Creanga et al. found that although traditional causes of pregnancy-related mortality continued to decline from 2006 to 2010, cardiovascular causes increased by 26.4%. Cardiac arrhythmias, including SVT, AF, and ventricular tachycardia are all important contributors to maternal cardiovascular morbidity and mortality. In a large administrative dataset, hospitalization for arrhythmia in pregnant women led not only to a higher rate of in-hospital death, 5.9% (compared with 0% in all women), but also led to a higher rate of maternal or fetal complications, 36.5% (compared to 21.8% in all women) [5].

Differential Diagnosis and Potential Pitfalls

Maternal mortality due to amniotic fluid embolism can overlap clinically with other causes of cardiorespiratory collapse, most notably hypovolemic shock secondary to postpartum hemorrhage, anesthetic accident, pulmonary thromboembolism, septic shock, and anaphylactic shock.89 Consequent clinical manifestations may therefore also overlap, including DIC and refractory hypotension. Pathologically, findings common to these conditions can include widespread visceral hemorrhage and early ischemic myocardial infarction. However, only amniotic fluid embolism will manifest the characteristic intravascular elements within small pulmonary vessels and within myometrial vasculature. Too, fibrin microthrombi should be absent in other viscera, unless perhaps profound and prolonged DIC has supervened before death.

Introduction

Maternal mortality in the United States is rising and is presently the highest in the developed world at an estimated rate of 26.4 deaths per 100,000 live births [1]. Maternal mortality has considerable racial and ethnic disparities, with even higher mortality in black non-Hispanic and American Indian/Alaskan Native women (Figure 1).

Death from cardiovascular disease (CVD) represents 26.5% of all pregnancy-related deaths in the United States [2]. The rising trend appears to be secondary to many contributing factors including increasing maternal age, rise in multifetal pregnancies, and the increased burden of preexisting cardiovascular risk factors in the pregnant population. In addition, survivors of childhood cancer, who have been exposed to cardiotoxic therapies, and women with congenital heart disease (CHD) are now able to pursue pregnancy due to advances in care.

Unlike many CVD processes, there are no randomized controlled data to support decision making, and guidelines are largely built on expert consensus. The care of the pregnant woman with heart disease also engages several disciplines including obstetrics, obstetric anesthesiology, and cardiology. These teams have different perspectives but a common goal: the delivery of a healthy fetus without maternal cardiac complications. It is therefore vital for cardiologists to continue to build on their knowledge on the management of CVD during pregnancy and work in a multidisciplinary fashion to improve care.

Hepatic

Maternal morbidity and mortality during pregnancy with chronic liver dysfunction is typically related to severity of the disease. The model for end-stage liver disease (MELD), a calculated score based on the international normalized ratio (INR), bilirubin, and serum creatinine, appears to correlate with antepartum complication rates; in one report, patients with a MELD score of ≤6 did not develop any significant hepatic complications [8]. Endoscopy of the upper gastrointestinal tract to screen for esophageal or gastric varices should be considered in patients with portal hypertension. Transjugular intrahepatic shunting, sclerotherapy, and endoscopic band ligation have been described during pregnancy, although concern for uterine ischemia has been raised with octreotide infusion sclerotherapy [9]. Because of the high risk of antepartum hemorrhage (38%–78%) with consequent mortality rate of 3%, presence of esophageal varices may represent a relative contraindication to conception [9].

Time Trends in Mortality Rates of the Perinatal Period in the United States

Maternal mortality and IM declined steadily through the 20th century. By 2000, neonatal mortality was 10% of its 1915 value, postneonatal mortality less than 7%, and maternal mortality less than 2%. The contribution to these changes of a variety of complex social factors, including improvements in income, housing, birth spacing, and nutrition, has been widely documented, as has the role of ecologic-level public health interventions that have produced cleaner food and water (Division of Reproductive Health, 1999). Public health action at the individual level, including targeted maternal and infant nutrition programs and immunization programs, has made a lesser but still notable contribution. Medical care per se was, until recently, less critically involved, with the exception of the decline in maternal mortality, which was very sensitive to the developments in blood banking and antibiotics that began in the 1930s. To this day hemorrhage and infection account for a large fraction of the world's maternal deaths (Khan et al., 2006).

A notable feature of the past half-century or so is the sharp decline in all three mortality rates beginning in the 1960s following a period of stagnation in the 1950s (Fig. 1.2) The decline began with maternal mortality, followed by postneonatal, and then neonatal. The contribution of medical care of the neonate was most clearly seen in national statistics in the 1970s, a decade that witnessed a larger decline in neonatal mortality than in any previous decade of the century. All of the change in neonatal mortality between 1950 and 1975 was in mortality for a given birthweight; no improvement was seen in the birthweight distribution (Lee et al., 1980). This finding suggested that the effectiveness of newborn intensive care has had a striking impact on mortality in very small babies. Prior to the development of newborn intensive care, survival at birthweights less than 1000 g was very rare. In 2013, the US survival rate to 1 year for infants with a birthweight between 501 and 999 g was 75%, and the number of survivors at age 1 was over 16,000.

In retrospect, three factors seem to have played critical roles in the rapid development of the newborn intensive care programs that largely accounted for the rapid decline in birthweight-specific neonatal mortality that characterized national trends in the last third of the 20th century. The first was the willingness of medicine to provide more than nursing care to marginal populations such as the premature infant. While the death of the mildly premature son of President Kennedy in 1963 provided a stimulus to the development of newborn intensive care, it should be noted that the decline in IM that began in the 1970s was paralleled by a similar decline in mortality for the extremely old (Rosenwaike et al., 1980). This was, perhaps, an indicator that the availability of federal funding through Medicare and Medicaid enabled previously underserved populations at the extremes of age to receive greater medical attention than they had before. The Medicaid program, adopted in 1965, may have made it feasible for the first time to pay for the intensive care of premature newborns, among whom the medically indigent are over-represented. While financial support for newborn intensive care may have been a necessary ingredient in its development, finances would have not been sufficient to improve neonatal mortality had not new medical technologies, especially those supporting ventilation of the immature newborn lung, been developed at about the same time (Gregory et al., 1975).

Advances in newborn care have ameliorated the impact of premature birth and birth defects on mortality. Unfortunately, the underlying disorders that drive perinatal mortality and the long-term developmental disorders that are sometimes their sequelae have shown no tendency to abate. With the very important exception of neural tube defects, whose prevalence has declined with folate fortification of flour in the United States and programs to encourage intake of folate in women of child-bearing age (Mathews et al., 2002), the major causes of death (preterm birth and birth defects) have not declined, nor has cerebral palsy, the major neuro-developmental disorder that can be of perinatal origin (Paneth et al., 2006). Progress has come from improved medical care of the high-risk pregnancy and the sick infant, rather than through understanding and prevention of the disorders themselves.

The pace of decline in infant, neonatal, and postneonatal mortality in the United States began to slow in 1995 and changed little in the following decade. A modest decline was seen, however, between 2005 and 2010 (Table 1.1). Data from the Vermont Oxford Neonatal Network encompassing more than a quarter of a million newborns from hundreds of largely North American neonatal units showed a decline in mortality of 12.2% for infants of 501–1500 g for 1990–1999 (Horbar et al., 2002) and a further 13.3% decline for 2000–2009 (Horbar et al., 2012). These declines are more modest than in the early days of newborn intensive care. From 1960–1985, a greater than 50% decline in mortality for infants of 501–1500 g was recorded in national data (Buehler et al., 1987; Prager, 1994), even though much of the first decade of that interval preceded the use of newborn intensive care technology in all but a few pioneering centers. The pace of advances in newborn medicine and the expansion of newborn intensive care to populations previously underserved, factors that have exerted a constant downward pressure on IM since the 1960s, have lessened in the past two decades or so.

Reported maternal mortality has actually climbed substantially in recent years, but this is almost certainly the effect of the improved reporting described above. The Centers for Disease Control (CDC) has a special unit dedicated to the problem of maternal mortality, the Pregnancy Mortality Surveillance System (CDC, 2017). Established in 1987, its counts of maternal deaths, based on more in-depth exploration than is possible from a vital registration system alone, have provided consistently higher estimates of maternal mortality than data reported by the NCHS, as shown in Fig. 1.2. Recognizing this, and the variation in reporting resulting from the variable use by states of the 2003 recommendation for identifying recent pregnancies on death certificates, the NCHS stopped reporting maternal mortality in 2008 (Minino et al., 2011). All recent maternal mortality data in the US are produced by the Pregnancy Mortality Surveillance System.

The risk of preterm birth (<37 weeks' gestation) increased steadily in the first years of the present century, peaked in 2007, and has declined by 8% since (Hamilton et al., 2015). The increase was largely in moderately preterm babies and likely reflected an increased willingness on the part of obstetricians to deliver fetuses earlier in gestation who were not doing well in utero, as well as the increased prevalence of twins and triplets, who are generally born preterm, resulting from in vitro fertilization. The newer data suggest a reversal of these earlier practices.

The recording of diabetes in pregnancy more than doubled from 1995 to 2010, but the NCHS has suggested that some of this might reflect more complete reporting on the 2003 birth certificate revision (Martin et al., 2010b). The differences in the two forms of birth certificate in circulation, and the uneven implementation of the newer version in vital registration areas, led NCHS, in 2008 (Martin et al., 2010a), to omit regular reporting of smoking, alcohol intake, weight gain, late prenatal care, and pregnancy-associated hypertension, among other variables, from its regular tabulations in annual natality reports, and these are not provided for 2010 in Table 1.1.

The cesarean section rate continues its long-term increase, from 5% in 1970 to 23% in 1990, peaking at nearly 33% in 2010, with a faint decline since (Hamilton et al., 2015). The reasons for this increase are multifactorial and include pressures from patients, physicians, and the medical malpractice system. The steady reduction in smoking in pregnancy is likely to be real, whereas trends in the self-reporting of alcohol use in pregnancy may be influenced by societal norms and expectations. Fewer women seem to have late or no prenatal care in recent years, but perhaps surprisingly, more women are found to have inadequate pregnancy weight gain at term. A very slight uptick in the fertility rate follows a long-term (since about 1960) decline in fertility in the United States. More than 4 in 10 mothers in the United States are now unmarried when they give birth.