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Overview of High-Risk Pregnancy

By

Raul Artal-Mittelmark

, MD, Saint Louis University School of Medicine

Last full review/revision Sep 2020| Content last modified Sep 2020
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In a high-risk (at-risk) pregnancy, the mother, fetus, or neonate is at increased risk of morbidity or mortality before, during, or after delivery.

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.

Maternal mortality ratios in selected countries

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

Usually, several factors contribute to maternal mortality (4). They include

  • Delay in seeking assistance by the patient and family

  • Lack of transportation

  • Delay in providing assistance at a health care facility

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

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

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

Table
icon

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

10

10

Postterm pregnancy (> 42 weeks)

10

Mild preeclampsia

5

5

Preterm labor at < 37 weeks

5

5

Secondary arrest of dilation

5

Labor > 20 hours (protracted labor)

5

Second stage > 2.5 hours

5

5

Precipitous labor (< 3 hours)

5

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):

  • Class I: 30–34.9

  • Class II: 35–39.9

  • Class III: > 40

BMI = body mass index; NYHA = New York Heart Association; STDs = sexually transmitted diseases.

Risk assessment reference

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