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Overview of High-Risk Pregnancy

By Raul Artal, MD

In a high-risk (at-risk) pregnancy, the mother, fetus, or neonate is at increased risk of morbidity or mortality before or after delivery.

In 2013, overall maternal mortality rate in the US was 28/100,000 deliveries; incidence is 3 to 4 times higher in nonwhite women. The maternal mortality rate is substantially 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 2013, ratios ranged from 1 (Belarus) to 980 (Chad) per 100,000 live births (countries not shown). The maternal mortality ratio is substantially higher in the US than in other Western countries.

Data from WHO, UNICEF, UNFPA, The World Bank, and the United Nations Population Division. Trends in Maternal Mortality: 1990 to 2013. Geneva, World Health Organization, 2014.

The most common causes of maternal death are

  • Hemorrhage

  • Preeclampsia

  • Pulmonary embolism

  • Infection

  • Complications of cardiovascular or other preexisting disorders

Nearly half of maternal deaths are preventable.

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 wk) and those during the early neonatal period (< 7 days after birth).

The most common causes of perinatal death are

  • Obstetric complications

  • Infection

  • Placental abnormalities

  • Congenital malformations

  • Preterm delivery

Risk Assessment During Pregnancy

Risk assessment is part of routine prenatal care. Risk is also assessed during or shortly after labor and at any time that events may modify risk status. Risk factors (see Table: Risk Factors for Complications During Pregnancy) 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. 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

Pregnancy Risk Assessment

Category

Risk Factors

Score*

Preexisting

Cardiovascular and renal disorders

Moderate to severe preeclampsia

10

Chronic hypertension

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

Thyroid disorders

5

Obesity class II

5

Gestational diabetes

5

Family history of diabetes

1

Obstetric history

Fetal exchange transfusion because of Rh incompatibility

10

Stillbirth

10

Late abortion (16–20 wk)

10

Postterm pregnancy (> 42 wk)

10

Preterm newborn (< 37 wk and < 2500 g)

10

Intrauterine growth restriction (weight < 10th percentile for estimated gestational age)

10

Abnormal fetal position

10

Polyhydramnios (hydramnios)

10

Multifetal pregnancy

10

Previous brachial plexus injury

10

Neonatal death

5

Cesarean delivery

5

Habitual ( 3) abortion

5

Neonate > 4.5 kg

5

Shoulder dystocia

5

Multiparity of > 5

5

Seizure disorders or cerebral palsy

5

Fetal malformations

1

Other disorders

Abnormal cervical cytologic findings

10

Sickle cell disease

10

Thrombophilia

10

Positive serologic results for STDs

5

Severe anemia (Hb < 9 g/dL)

5

History of TB or purified protein derivative injection site induration 10 mm

5

Pulmonary disorders

5

Mild anemia (Hb 9.0–10.9 g/dL)

1

Anatomic abnormalities

Uterine malformation

10

Insufficient (incompetent) cervix

10

Small pelvis

5

Maternal characteristics

Age 35 or 15 yr

5

Weight < 45.5 or > 91 kg

5

Psychiatric disorder or intellectual disability

1

Antepartum

Exposure to teratogens

Group B streptococcal infections

10

Certain viral infections (eg, rubella, cytomegalovirus infections)

5

Flu syndrome (severe)

5

Excessive use of drugs

5

Smoking 1 pack/day

1

Alcohol (moderate to severe)

1

Pregnancy complications

Preterm labor at < 37 wk

10

Preterm premature rupture of membranes

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

Uterine rupture

10

Postterm (> 42 wk)

10

Mild preeclampsia

5

Premature rupture of membranes > 12 h

5

Preterm labor at ≥ 37 wk

5

Primary dysfunctional labor

5

Secondary arrest of dilation

5

Labor > 20 h

5

Second stage > 2.5 h

5

Medical induction of labor

5

Precipitous labor (< 3 h)

5

Primary cesarean delivery

5

Repeat cesarean delivery

5

Elective induction of labor

1

Prolonged latent phase

1

Oxytocin augmentation

1

Placental

Placenta previa

10

Abruptio placentae

10

Chorioamnionitis

10

Fetal

Abnormal presentation (breech, brow, face) or transverse lie

10

Multifetal pregnancy

10

Fetal bradycardia > 30 min

10

Prolapsed cord

10

Fetal weight < 2.5 kg

10

Fetal weight > 4 kg

10

Fetal acidosis pH 7

10

Fetal tachycardia > 30 min

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:

  • Class I: 30–34.9

  • Class II: 35–39.9

  • Class III: > 40

NYHA = New York Heart Association; STDs = sexually transmitted diseases.

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