The subspecialty of obstetric anesthesia has made tremendous efforts in the area of patient safety. Obstetric anesthesiologists have documented their practices and followed up on efforts to improve them. For example, three workforce surveys have documented how care is provided and hospitals are staffed in low and high volume delivery services (1). Obstetric anesthesiologists have updated the American Society of Anesthesiologists (ASA) practice guidelines, with evidence-based recommendations for care (2). There are published reviews of anesthesia-related maternal mortality from international (3), national (4), and state (5) sources that document how adverse outcomes occur so anesthesiologists can address and prevent them. The ASA Closed Claims Project database has extracted the obstetric anesthesia liability cases for review, reflection, and improvement of care (6). Team training and simulation have been used to improve performance in emergency situations on labor and delivery (7). Patient safety has clearly been at the forefront of obstetric anesthesia care. This chapter will review our understanding of maternal morbidity and mortality, both current status and areas where efforts can be focused to achieve further improvement.

The Centers for Disease Control and Prevention (CDC) published their U.S. maternal mortality data from 1991 to 1997 in 2003 (8). They noted that although death from complications of pregnancy has decreased by 99% since 1900, there have been no further decreases in the last two decades. In the 2003 report there were 4,200 pregnancy-related deaths with an overall mortality ratio of 11.8 deaths per 100,000 live births, a substantial increase from the 7 to 8/100,000 reported since 1982. In 1999 the national maternal mortality rate was 13.2 deaths per 100,000 live births. The appearance of an increase may be due to better methods of ascertainment, but it is certainly not decreasing and is still far from the Healthy People 2010 objective for maternal mortality of 3.3/100,000 live births. Those at greatest risk in their report were women of black race, women >34 years of age, and women who received no prenatal care. Among women who died after a live birth, the leading causes of death were embolism and hypertensive disorders of pregnancy.

A maternal death is devastating to all involved; after all, only in the obstetric patient can mortality be 200%. The most recent CDC report that reviewed US maternal mortality from 1998 to 2005 showed that although infant mortality has declined steadily due to increased survival of preterm infants and prevention of Sudden Infant Death Syndrome (SIDS), maternal mortality has not declined reaching 14.5/100,000 live births (9). This is the highest aggregate pregnancy-related mortality ratio of any period in the previous 20 years. Reasons for the lack of improvement are unclear but may include an actual increase, changes in coding from ICD-9 to ICD-10 and improved ascertainment from linkage of death certificates to live birth and fetal death certificates. Mortality remains 3 to 4 times higher for African-American women than white women. The causes of pregnancy-related deaths are shown in Figure 46-1. Non-cardiovascular medical conditions are now the most common cause of death (13% of deaths), followed by hemorrhage (12%), hypertensive disorders of pregnancy (12%), cardiovascular conditions (12%), cardiomyopathy (11%), infection (11%), and thrombotic pulmonary embolism (10%). Since their last report (8), deaths due to hemorrhage and hypertension continue to decrease, while those due to medical conditions, especially cardiac, continue to increase. Among deaths after a live birth, hypertensive disorders of pregnancy, cardiomyopathy, non-cardiovascular medical conditions and cardiovascular conditions were most common. Anesthetic deaths account for 1.2% of maternal deaths, and have fallen to tenth among the most common causes of maternal mortality in the United States (Table 46-1).

Since 1991, the United States’ CDC has defined maternal deaths as those that occur within 1 year of delivery (rather than the 42 days used previously) and that are related to the pregnancy (10). By extending the definition to 1 year after delivery, the percentage of deaths due to cardiomyopathy increased because those deaths often occur after a lengthy illness, but are still related to the pregnancy. Many maternal deaths (perhaps over 30%) are missed because the cause of death on the death certificate does not include the fact that she was pregnant. For example, if a woman dies of a pulmonary embolism but the death certificate does not record that she was pregnant, it would not be classified as a maternal death. The CDC asks states to link maternal death certificates with live birth or fetal death certificates, thus increasing identification of maternal deaths. This increased ascertainment may be the reason for an apparent increase in pregnancy-related deaths.

In the United States mothers are having their children at older ages. How does the change in demographics affect outcomes? Using the CDC database, investigators looked at maternal mortality in women having children after age 35 (11) and after age 50 (12). Although the actual risk of mortality was low, the risk ratio for deaths in all categories (hemorrhage, embolism, hypertension, cardiomyopathy, etc.) was increased after age 35. The authors note “… it is clear that for both the woman and her fetus, achieving pregnancy before age 35 is the safest course to follow.” There were only 539 births among women aged 50 and older, but the risk of
preterm labor and low birth weight was higher, leading to increased fetal morbidity and mortality. Physicians have little or no control over the age when women choose to become pregnant, but they can certainly have more awareness of the increased risk to the mother when they are over age 35.

Ascertainment may also be improved when access to medical records is improved. A very large retrospective review of maternal deaths in a large US health care delivery system (HCA, the Hospital Corporation of America) examined the details of 95 maternal deaths in 1.5 million deliveries (6.5 deaths per 100,000 pregnancies) between 2000 and 2006 (13). Leading causes of death were preeclampsia, pulmonary thromboembolism, amniotic fluid embolism, hemorrhage, and cardiac disease. The most common preventable causes were failure to adequately control blood pressure in hypertensive women, failure to adequately diagnose and treat pulmonary edema in women with preeclampsia, failure to pay attention to vital signs following cesarean delivery, and hemorrhage following cesarean delivery. Rate by mode of delivery was strikingly different: 0.2/100,000 for vaginal and 2.2/100,000 for cesarean deliveries, or 11 times higher during cesarean delivery. That is a sobering statistic as cesarean delivery rates continue to rise and operative deliveries may be done solely for maternal request. Anesthesia is not listed as a cause of death in their series, but a personal communication with the author indicated there were two deaths attributed to anesthetic management. One involved an unrecognized intravascular injection of local anesthetic through an epidural catheter and the second involved an anaphylactic reaction to antibiotics given by the anesthesiologist at the time of cesarean delivery. The conclusions from their study were that most maternal deaths in the United States are not preventable and occur in low risk pregnancies. Segregating delivery services into high and low risks will never be completely successful. The authors also state that universal thromboembolism prophylaxis for cesarean deliveries is the best way to decrease maternal mortality, but add that since neuraxial anesthesia is the most common anesthetic technique for cesarean delivery, pneumatic compression devices should be used in preference to anticoagulation.

A perinatal network of physicians was also able to do a detailed evaluation of their cases of maternal mortality, “near miss” morbidity, and severe morbidity (14). The data showed that 41% of the deaths, 46% of the “near misses,” and 17% of the severe morbidities should have been preventable. Cardiac causes, stroke, and embolic diagnoses were higher among the deaths. Hemorrhage and infection were highest in the near-miss group, and preeclampsia was highest in the severe morbidity group. Patient factors were involved in 13% to 20%, systems issues in 33% to 47%, and provider issues in 90%. In all groups, incomplete or inappropriate management was cited as the major factor.

Other perinatal networks are also attempting to gather more complete data on maternal mortalities. A review of maternal deaths from 1992 to 1998 in a 10-hospital urban perinatal network in the United States found a strikingly higher maternal mortality ratio than that reported nationally; 22.8 maternal deaths per 100,000 live births rather than the reported national rate at the time of 7.5/100,000 (15). The group was able to identify all maternal deaths in their perinatal network, and because they formed a peer-review committee, they were able to review each case in detail. The deaths were deemed potentially preventable in 37%, and there was a provider factor identified in >80%. Pulmonary embolus and cardiac disease together accounted for 40% of the pregnancy-related deaths. There was only one anesthesia-related death, and it was attributed to central nervous system depression in a patient who was receiving multiple narcotics, as well as other potentially depressive medications during labor.

Using similar methodology, a state-maintained database was used to determine the incidence and causes of maternal mortality (16). They reported a high overall delivery mortality rate of 16.4/100,000 live births, which they also attributed to improved detection. Anesthesia-related mortality
accounted for 5.2% of the deaths. Unfortunately, since it was an anonymous database, no further information could be obtained about the specifics of each case. Perinatal networks and state maternal mortality committees are able to more accurately identify all maternal deaths in their area and may provide more in-depth information to use in prevention programs.

A state maternal mortality committee in North Carolina identified all pregnancy-related deaths between 1995 and 1999, and determined the incidence of preventable deaths (17). Overall, 40% of deaths were preventable, but almost all deaths due to hemorrhage or exacerbation of a chronic disease were considered preventable. In contrast, almost none of the deaths due to amniotic fluid embolism or stroke were preventable. The most frequent cause of death was comorbidity associated with cardiomyopathy. Race was another factor that also influenced outcome. Among African-American women, 46% of deaths were potentially preventable compared to 33% of deaths among white women. The mortality ratio was 42/100,000 live births among African Americans, as compared to 12.3/100,000 among whites.

To summarize the common themes in all-cause maternal mortality studies:

Even when anesthesia is not the direct cause of death, anesthetic care contributes to the quality of the outcomes. The 2003–2005 Confidential Enquiry into Maternal and Child Health reviewed maternal deaths and found 31 cases due to other causes in which anesthesia contributed (3). These contributions included failure of the anesthesiologist to recognize serious illness or comorbidities, less than optimal anesthetic management of hemorrhage including delayed diagnosis, poor resuscitation in sepsis, inadequate control of hypertension in preeclampsia, and issues related to maternal obesity. Obstetric anesthesiologists must be prepared to handle disastrous complications associated with hemorrhage, thrombotic or amniotic fluid embolism, hypertension and sepsis as well as maternal coexisting diseases. Peripartum hemorrhage requires participation from everyone on the labor and delivery team.

A study of the epidemiology of postpartum hemorrhage in the United States from 1995 to 2004 found that postpartum hemorrhage complicated 2.9% of all deliveries and was associated with 19% of all in-hospital deaths after delivery (18). Although hemorrhage due to placental abnormalities can be severe, atony accounts for 79% of cases. Risk factors for uterine atony include age <20 or >40, cesarean delivery, hypertensive disorders, polyhydramnios, chorioamnionitis, multiple gestation, retained placenta, and antepartum hemorrhage, but other than extremes of age and cesarean delivery, risk factors were present in only 39% of cases. In other words, postpartum hemorrhage caused by uterine atony resulting in transfusion often occurs in the absence of recognized risk factors. Another cause of peripartum hemorrhage is uterine rupture. A review of 41 cases of uterine rupture found that only half occurred in women with a prior cesarean delivery, and of the remaining cases, only one-third had had uterine surgery of other types (19). Nine uterine ruptures occurred before labor and the rest during labor. Results of studies such as these point out that parturients at risk of serious hemorrhage may be difficult to identify. Hospitals must adopt protocols for management of postpartum hemorrhage that include medications, operative and non-operative maneuvers, and massive transfusion protocols to guide care and prevent treatment delays.

Two studies reviewed obstetric morbidity in the United States. The first examined severe obstetric morbidity from 1998 to 2005 from the Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project (20). They found that complications increased from 0.64% to 0.81% of delivery hospitalizations, with significant increases in renal failure, pulmonary embolism, adult respiratory distress syndrome, shock, blood transfusion, and ventilation. Increases paralleled the rising cesarean delivery rate during this time. Maternal age, parity, multiple births, and most comorbidities did not contribute to these outcomes. Only the increases in pulmonary embolism and blood transfusion were not accounted for by the rise in cesarean delivery rates from 21% to 30%. The second study used the National Hospital Discharge Survey data to estimate rates of intrapartum morbidity during 2001 to 2005 and compared them with rates during 1993 to 1997 (21). They did not find an increase in intrapartum obstetric complications even though the cesarean delivery rate increased from 21.8% to 28.3%. Rates of pregnancies complicated by preexisting medical conditions such as chronic hypertension, preeclampsia, gestational and preexisting diabetes, asthma and postpartum hemorrhage did increase by 20%, while rates of third- and fourth-degree lacerations and some infections decreased.

The epidemiology of maternal morbidity and mortality due to a direct anesthetic cause has been reviewed in several ways. The Healthcare Cost and Utilization Project State Inpatient Database was used to identify women in the New York state who experienced an anesthesia-related complication during labor and delivery from 2002 to 2005 (22). Significant risk factors for an anesthetic complication were cesarean delivery, rural area, preexisting medical condition, Caucasian race, and scheduled admission. Anesthetic complications occurred in 0.46% of women, but when complications occurred, mortality increased 22-fold. Spinal headache accounted for a third of the complications. Anesthesia-related causes of maternal mortality have become so uncommon, they are rarely mentioned in studies of all-cause maternal mortality. Data from the CDC shows that anesthesia-related maternal mortality in the United States has fallen by 59% since 1979 and stabilized at about 1 death per million live births (4). Results from the triennial reports in the United Kingdom are similar (Table 46-2).

In 1987 the CDC established an ongoing National Pregnancy Mortality Surveillance System to monitor maternal deaths at the national level and conduct epidemiologic studies of the deaths of pregnant women (23). Health departments in all 50 states, the District of Columbia, and New York City provide the CDC with copies of maternal death certificates with patient and provider identification removed. When available, linked birth certificates or fetal death records are also provided. These records are available since 1979 (4). The CDC has no legal ability to obtain medical records, autopsy reports, or other information that could provide detailed data, but some conclusions can be made. Using national statistics on cesarean delivery rates, the number of
deaths reported to the CDC in each year, and estimates of the proportion of cesarean deliveries done under regional or general anesthesia each year (1), case fatality rates and risk ratios by type of anesthesia can be calculated (Table 46-3). In the 1980s, general anesthesia for cesarean delivery appeared to be much riskier than regional anesthesia. Since then, deaths associated with general anesthetics appear to be declining, while deaths associated with regional anesthesia may be increasing.