In 2017, overall maternal mortality rate in the US was 19/100,000 deliveries, as estimated by the WHO; incidence is 3 to 4 times higher in nonwhite women. Almost 50% of pregnancy-associated deaths in the US occur in non-Hispanic black women. The maternal mortality rate is higher in the US than in other Western countries (eg, Germany, Netherlands, Poland, Spain, Sweden, Switzerland, United Kingdom).
Maternal mortality ratios in selected countries
|
Maternal mortality ratio refers to the number of women who die from pregnancy-related causes during pregnancy or within 42 days of the end of the pregnancy per 100,000 live births. In 2017, ratios ranged from 2 (Poland) to 1150 (South Sudan) per 100,000 live births (countries not shown). The maternal mortality ratio is higher in the US than in other Western countries. Data from the World Health Organization, United Nations Children’s Fund (UNICEF), United Nations Population Fund (UNFPA), The World Bank, and the United Nations Population Division. Trends in Estimates of Maternal Mortality Ratio (MMR; Maternal Deaths per 100,000 Live Births) 2000–2017. Geneva, World Health Organization, 2019. 
|
Disparities by race and ethnicity in maternal mortality are significant worldwide. In the US, the maternal mortality rate is 3.3 times higher in black women and 2.5 times higher in American Indian and Alaska native women than in white women (1). In Brazil, the maternal mortality is about 5 times higher in women of African descent than in white women; in the United Kingdom, it is higher in black women than in white women (2).
Maternal death statistics include direct obstetric and indirect causes (3).
The most common causes of maternal death worldwide are
-
Hemorrhage (27.1%)
-
Hypertensive disorders, including preeclampsia (14.1%)
-
Sepsis (10.7%)
-
Abortion, including induced abortion, miscarriage, and ectopic pregnancy ( ≥ 8%)
-
Pulmonary embolism (3%)
-
Other disorders (eg, preexisting disorders such as obesity, operative delivery, and infectious diseases (eg, HIV infection)
Usually, several factors contribute to maternal mortality (4). They include
About 3 of 5 maternal deaths are preventable (1).
Perinatal mortality rate in offspring in the US is about 6 to 7/1000 deliveries; deaths are divided about equally between those during the late fetal period (gestational age > 28 weeks) and those during the early neonatal period (< 7 days after birth).
The most common causes of perinatal death are
-
Maternal disorders (eg, hypertension, diabetes mellitus, obesity, autoimmune disorders)
-
Infection
-
Genetic abnormalities in the fetus
-
Congenital malformations
Other maternal characteristics that increase the risk of perinatal mortality include maternal age (much younger or older than average), unmarried status, smoking, and multiple gestations.
References
-
1. Petersen EE, Nicole L. Davis NL, Goodman D, et al: Vital Signs: Pregnancy-related deaths, United States, 2011–2015, and strategies for prevention, 13 states, 2013–2017. MMWR Morb Mortal Wkly Rep 68 (18): 423–429, 2019. doi: 10.15585/mmwr.mm6818e1
-
2. Small M, Allen T, Brown HL: Global disparities in maternal morbidity and mortality. Semin Perinatol 41 (5): 318–322, 2017. doi: 10.1053/j.semperi.2017.04.009
-
3. Say L, Chou D, Gemmill A, et al: Global causes of maternal death: A WHO systematic analysis. Lancet Glob Health 2 (6) :e323–33, 2014. doi: 10.1016/S2214-109X(14)70227-X
-
4. Building U.S. Capacity to Review and Prevent Maternal Deaths: Report from Nine Maternal Mortality Review Committees.
Risk Assessment During Pregnancy
Risk assessment is part of routine prenatal care. Family history and genetic evaluation are especially important. Risk is also assessed during or shortly after labor and at any time that events may modify risk status. Risk factors are assessed systematically because each risk factor present increases overall risk.
Several pregnancy monitoring and risk assessment systems are available. The most widely used system is the Pregnancy Assessment Monitoring System (PRAMS), which is a project of the Centers for Disease Control and Prevention (CDC) and state health departments. PRAMS provides information for state health departments to use to improve the health of mothers and infants. PRAMS also enables the CDC and states to monitor changes in health indicators (eg, unintended pregnancy, prenatal care, breastfeeding, smoking, drinking, infant health).
High-risk pregnancies require close monitoring and sometimes referral to a perinatal center, especially if women have complex high-risk conditions. These centers offer many specialty and subspecialty services, provided by maternal, fetal, and neonatal specialists (1). When referral is needed, transfer before rather than after delivery results in lower neonatal morbidity and mortality rates.
The most common reasons for referral before delivery are
-
Preterm labor (often due to premature rupture of the membranes)
-
Preexisting or developing disorders (eg, diabetes, hypertension, severe [morbid] obesity)
Pregnancy Risk Assessment
Category |
Risk Factors |
Score* |
Preexisting |
||
|
Cardiovascular and renal disorders |
Moderate to severe preeclampsia |
10 |
|
10 |
||
|
Moderate to severe renal disorders |
10 |
|
|
Severe heart failure (class II–IV, NYHA classification) |
10 |
|
|
History of eclampsia |
5 |
|
|
History of pyelitis (infection of the renal pelvis) |
5 |
|
|
Mild heart failure (class I, NYHA classification) |
5 |
|
|
Mild preeclampsia |
5 |
|
|
Acute pyelonephritis |
5 |
|
|
History of cystitis |
1 |
|
|
Acute cystitis |
1 |
|
|
History of preeclampsia |
1 |
|
|
Metabolic disorders |
†Obesity class III |
10 |
|
Insulin-dependent diabetes |
10 |
|
|
Previous endocrine ablation |
10 |
|
|
5 |
||
|
†Obesity class II |
5 |
|
|
Gestational diabetes |
5 |
|
|
Family history of diabetes |
1 |
|
|
Obstetric history |
Fetal exchange transfusion because of Rh incompatibility |
10 |
|
10 |
||
|
Late abortion (16–20 weeks) |
10 |
|
|
Postterm pregnancy (> 42 weeks) |
10 |
|
|
Preterm newborn (< 37 weeks and < 2500 g) |
10 |
|
|
Intrauterine growth restriction (weight < 10th percentile for estimated gestational age) |
10 |
|
|
10 |
||
|
Polyhydramnios (hydramnios) |
10 |
|
|
10 |
||
|
Previous brachial plexus injury |
10 |
|
|
Neonatal death |
5 |
|
|
5 |
||
|
Habitual (≥ 3) abortion (recurrent pregnancy loss) |
5 |
|
|
Neonate > 4.5 kg |
5 |
|
|
5 |
||
|
Multiparity of > 5 |
5 |
|
|
5 |
||
|
1 |
||
|
Other disorders |
Abnormal cervical cytologic findings |
10 |
|
10 |
||
|
Thrombophilia |
10 |
|
|
10 |
||
|
Positive serologic results for STDs |
5 |
|
|
Severe anemia (hemoglobin < 9 g/dL [90 g/L) |
5 |
|
|
History of tuberculosis or purified protein derivative injection site induration ≥ 10 mm |
5 |
|
|
Pulmonary disorders |
5 |
|
|
Mild anemia (hemoglobin 9.0–10.9 g/dL [90–109 g/L) |
1 |
|
|
Uterine malformation |
10 |
|
|
10 |
||
|
Small pelvis |
5 |
|
|
Maternal characteristics |
Age ≥ 35 or ≤ 15 years |
5 |
|
Weight < 45.5 or > 91 kg (obesity class III) |
5 |
|
|
Psychiatric disorder or intellectual disability |
1 |
|
Antepartum |
||
|
Exposure to teratogens |
10 |
|
|
Smoking > 10 cigarettes/day (associated with premature rupture of membranes) |
10 |
|
|
Certain viral infections (eg, rubella, cytomegalovirus infections) |
5 |
|
|
Flu syndrome (severe) |
5 |
|
|
Alcohol (moderate to severe) |
1 |
|
|
Pregnancy complications |
Preterm labor at < 37 weeks |
10 |
|
10 |
||
|
Rh sensitization only (not requiring an exchange transfusion) |
5 |
|
|
Vaginal spotting |
5 |
|
Intrapartum |
||
|
Maternal |
Moderate to severe preeclampsia |
10 |
|
Polyhydramnios (hydramnios) or oligohydramnios |
10 |
|
|
10 |
||
|
Postterm pregnancy (> 42 weeks) |
10 |
|
|
Mild preeclampsia |
5 |
|
|
Premature rupture of membranes> 12 hours |
5 |
|
|
Preterm labor at < 37 weeks |
5 |
|
|
Primary dysfunctional labor |
5 |
|
|
Secondary arrest of dilation |
5 |
|
|
Labor > 20 hours (protracted labor) |
5 |
|
|
Second stage > 2.5 hours |
5 |
|
|
Medical induction of labor |
5 |
|
|
Precipitous labor (< 3 hours) |
5 |
|
|
Primary cesarean delivery |
5 |
|
|
Repeat cesarean delivery |
5 |
|
|
Elective induction of labor |
1 |
|
|
Prolonged latent phase |
1 |
|
|
Oxytocin augmentation |
1 |
|
|
Placental |
10 |
|
|
10 |
||
|
10 |
||
|
Fetal |
Abnormal presentation (breech, brow, face) or transverse lie |
10 |
|
10 |
||
|
Fetal bradycardia > 30 minutes |
10 |
|
|
10 |
||
|
Fetal weight < 2.5 kg |
10 |
|
|
Fetal weight > 4 kg |
10 |
|
|
Fetal acidosis pH ≤ 7 |
10 |
|
|
Fetal tachycardia > 30 minutes |
10 |
|
|
Operative delivery using vacuum extractor or forceps |
5 |
|
|
Breech delivery, spontaneous or assisted |
5 |
|
|
* A score of 10 or more indicates a high risk. |
||
|
† National Institutes of Health's obesity classes based on BMI (kg/m2): |
||
|
BMI = body mass index; NYHA = New York Heart Association; STDs = sexually transmitted diseases. |
||
Risk assessment reference
-
1. American College of Obstetricians and Gynecologists: Levels of maternal care: Obstetric care consensus No. 9. Obstet Gynecol 134(2):428-434, 2019. doi: 10.1097/AOG.0000000000003384
