This edition of the ASA Monitor is focused on 30-day postoperative mortality. A search for “30-day mortality” and “obstetrics” on PubMed returns no results! Perhaps women don’t die after labor and delivery. However, the publication of more than 52,000 articles on “maternal mortality” and the building of the Taj Mahal in honor of a woman who died in childbirth suggest otherwise.
Maternal perinatal mortality is defined by the International Classification of Diseases (ICD-10) as maternal death during pregnancy and within 42 days after termination of pregnancy. Death must be related to or aggravated by pregnancy. Thus, a pregnant woman hit by a bus would not be included. The search term “maternal perinatal mortality” returns thousands of references.
The statistics
Globally, maternal mortality rates have significantly declined in recent decades. The maternal mortality ratio (the number of maternal deaths per 100,000 live births) has decreased by 34% (asamonitor.pub/3VjeD4Z). The reduction in maternal mortality ratio has been the largest in low- and middle-income countries, with maternal death reduced by 33% between 2000 and 2020.
“Significant disparities in maternal death rates exist worldwide. In high-income countries, one in 5,400 women will die of a pregnancy-related cause. In low-income countries, the ratio is one in 45.”
In 2020, 800 pregnant women died in the United States (asamonitor.pub/3TbNwGi). Nearly all (95%) were preventable (asamonitor.pub/3VjeD4Z). It is unacceptable and frightening that hundreds of pregnant women are dying from preventable deaths in the U.S.
Significant disparities in maternal death rates exist worldwide. In high-income countries, one in 5,400 women will die of a pregnancy-related cause. In low-income countries, the ratio is one in 45 (J Perinat Med 2022;51:170-81). Sub-Saharan Africa and Southern Asia accounted for around 87% of the estimated global maternal deaths in 2020 (asamonitor.pub/3VjeD4Z; asamonitor.pub/3TbNwGi; J Perinat Med 2022;51:170-81).
Figure 1: Maternal mortality, life expectancy, and births attended by skilled health personnel in high-income countries, lower-middle-income countries, low-income countries, Small Island Developing States, and Sub-Saharan Africa (J Perinat Med 2007;35:263-5; J Perinat Med 2022;51:170-81).
Unlike most low- to middle-income countries and other high-income countries, the maternal mortality ratio in the U.S. increased from eight out of 100,000 in 1990 to 20 in 2019 (MMWR Morb Mortal Wkly Rep 1995;44:6-7,13-4). The ratio further increased to 33 in 2021, partly related to the COVID epidemic (NCHS Health E-Stats;2023).
While the most common causes of maternal death, such as hemorrhage, hypertensive disorders of pregnancy, thromboembolism, and anesthesia complications, have declined, deaths related to chronic diseases have increased, particularly those secondary to cardiovascular diseases.
The two- to three-times higher maternal mortality ratios experienced by Black and Native American/Alaskan women compared to White, Hispanic, and Asian/Pacific Islander women have persisted through decades (Annu Rev Med 2023;74:199-216). Although there is significant variability in maternal mortality in the U.S. related to race/ethnicity and region that is independent of socioeconomic status, much of it is directly attributable to socioeconomic disparities (Annu Rev Med 2023;74:199-216). This portion appears directly related to lack of access to health care. The regional disparity evident within the U.S. is particularly notable in women who live in Arkansas, Kentucky, and Alabama (Figure 2) (Annu Rev Med 2023;74:199-216).
Figure 2: Maternal mortality within 42 days of termination of pregnancy, by state, 2018 (Annu Rev Med 2023;74:199-216).
Causes of maternal mortality
The most common causes of maternal mortality are hemorrhage, hypertension, embolism, sepsis, abortion, and indirect causes. Preexisting conditions to indirect causes include trauma and exacerbation of conditions such as HIV/AIDS, cardiovascular disease, and diabetes. Areas where abortion is restricted have a greater percentage of maternal death (asamonitor.pub/438NT99).
Risk factors in the U.S.
Multiple risk factors contribute to the increased maternal mortality rate in the U.S. Advancing maternal age is a significant factor that correlates with the risk of development of chronic conditions. Common chronic conditions such as hypertension, type 2 diabetes, heart disease, chronic kidney disease, lupus, asthma, and thyroid disease are more common in older mothers. Women with one of the above chronic conditions have a threefold higher risk of severe maternal morbidity or mortality than those without these conditions (Annu Rev Med 2023;74:199-216). Obesity and metabolic syndrome further increase the overall risk of developing pregnancy complications secondary to chronic diseases.
Prevention and risk mitigation
In the best of all possible settings, the woman’s caregiver would address risk prevention before conception when the desire to optimize health may be high. Treatment of chronic diseases, along with improved diet and weight management, can be optimized prior to conception. Stopping unhealthy habits, including tobacco and other drug use, may be more addressable due to the consideration of a healthy pregnancy. Such interventions are not possible in the approximate 50% of pregnancies that are unplanned (Lancet 2013;382:1807-16).
Weight management is a challenging but possibly alterable lifestyle factor (Best Pract Res Clin Obstet Gynaecol 2024;92:102435). Being overweight or obese (BMI >30) are clear risk factors for adverse pregnancy outcomes, including pregnancy loss. Gestational diabetes mellitus (GDM) is associated with preeclampsia, cesarean delivery, and postpartum hemorrhage. A 10% increase in pre-pregnancy BMI was associated with at least a 10% higher risk of preeclampsia, GDM, preterm delivery, and stillbirth (AM J Clin Nutr 2012;96:289-95). Pre-pregnancy adoption of a healthy diet, such as an alternate Mediterranean diet or a dietary approach to stop hypertension, has been shown to reduce incidence of GDM and preeclampsia (AM J Clin Nutr 2012;96:289-95; Am J Clin Nutr 2020;112:1429-37).
In addition to weight optimization, care regarding micronutrients is essential. The importance of folic acid has been consistently supported by multiple studies and is recommended by the World Health Organization and the American College of Obstetricians and Gynecologists (ACOG). It is known to reduce the risk of low birth weight and the frequency of preterm birth (Annu Rev Med 2023;74:199-216).
Physical activity during pregnancy has been evaluated in many randomized trials. Some women are concerned that exercise may have adverse effects on their pregnancy or cause miscarriage. This is exactly backward. Moderate to vigorous physical activity during pregnancy significantly reduces the risk of gestational diabetes, gestational hypertension, and preeclampsia. ACOG recommends moderate physical activity during pregnancy and postpartum (Obstet Gynecol 2020;135:e178-88).
Hypertensive disorders during and after pregnancy
It is critically important to address hypertensive disorders during pregnancy. Hypertension during pregnancy is also an important warning sign for future health. The incidence of cardiovascular disease is increasing in young women 35-44 years old. Hypertensive and other life-threatening disorders of pregnancy are strongly associated with chronic hypertension cardiac events and premature death (J Am Coll Cardiol 2021;77:1302-12). This strong association, beginning in some settings shortly after delivery, makes evaluation and management of hypertension important in women who have had hypertensive disease during pregnancy. The association is particularly strong in women who have had preeclampsia that leads to delivery.
Postpartum risk is reduced by maintaining a healthy weight and exercising (Best Pract Res Clin Obstet Gynaecol 2024;92:102435). Gestational diabetes, idiopathic preterm birth, fetal growth restriction, and placental abruption are also associated with future cardiovascular disease. A woman with any of these risk factors should be followed carefully for cardiovascular disease after delivery (Best Pract Res Clin Obstet Gynaecol 2024;92:102435).
One-fifth of maternal mortality happens in the first six weeks postpartum, sometimes referred to as the fourth trimester. As expected, cardiovascular disease, including peripartum cardiomyopathy, accounts for most of this postpartum mortality (Annu Rev Med 2023;74:199-216; Journal of Women’s Health 2018;27).
Maternal perinatal mortality is frighteningly high and increasing in the U.S. Thankfully, it is decreasing in most middle- and low-income countries. The increase in the U.S. is partially related to delayed childbearing age and development of chronic diseases. Maternal perinatal mortality in the U.S. reflects considerable racial, ethnic, socioeconomic, and regional disparities. Some of the risks of mortality can be addressed before pregnancy, including weight loss, increased exercise, improved management of chronic disease, and cessation of unhealthy habits. The anesthesiologist plays a vital role in managing patients in prepartum consultation, in the labor room, and in later life when perinatal risk factors are manifest. Our ability to understand and synthesize multiple aspects of a patient’s life in short order makes us uniquely able to reduce postpartum maternal mortality.