High-risk obstetrics

1

Define high-risk pregnancy.

High-risk pregnancies are those that involve either a maternal or fetal condition that increases the likelihood of maternal or fetal morbidity and/or mortality. They comprise approximately 6% to 18% of total pregnancies ( Table 56.1 ); however, the true incidence and particular comorbidity is highly dependent up on the demographic, socioeconomic status, and geographic region. Specifically, high-risk pregnancy is associated with age (< 15 or > 35 years old), lower socioeconomic status, rural areas, and lower educational achievement.

2

How many women die per day from pregnancy? What are the most common causes of death because of pregnancy?

The World Health Organization reports (2017 data) that approximately 810 women die every day (~ 300,000 per year) from preventable causes related to pregnancy, of which 94% of maternal deaths occur in low income countries (i.e., sub-Saharan Africa and Southern Asia). Common causes of pregnancy-related death include hemorrhage, infection, stroke, thrombotic pulmonary embolism, and cardiac disease. The most common cause of death in low-income countries is hemorrhage, whereas cardiac disease is the most common cause of death in high-income countries. The risk of pregnancy-related death is 1:45 in low-income countries compared with 1:5400 in high-income countries.

3

What are the hypertensive disorders of pregnancy?

Hypertensive disorders complicate up to 10% of pregnancies and are one of the leading causes of maternal morbidity and mortality worldwide. Chronic hypertension (HTN) is often diagnosed prepregnancy, but may go undiagnosed until the first prenatal visit. Chronic HTN is defined as HTN (i.e., > 140/90 mm Hg) before 20 weeks' gestation and does not resolve postpartum. Alternatively, gestational HTN is defined as HTN occurring after 20 weeks' gestation and does resolve postpartum. Neither presents with proteinuria. Preeclampsia is defined as new onset HTN after 20 weeks’ gestation presenting with either proteinuria (≥ 300 mg/24 h, protein-creatinine ratio ≥ 0.3, or 2 + on urine dipstick) or other evidence of severe features, such as the following:

• a.

  Thrombocytopenia

• b.

  New-onset headache or visual disturbances

• c.

  Impaired liver function

• d.

  Serum creatinine > 1.1 mg/dL or > 2 times baseline

• e.

  Pulmonary edema

Preeclampsia may initially present as gestational HTN and up to 50% of women with gestational HTN later develop proteinuria or other severe features consistent with the diagnosis of preeclampsia. If preeclampsia is left untreated, it can progress to eclampsia (defined by seizures). Table 56.2 summarizes the types of hypertensive disorders found in pregnant patients.

4

Describe the characteristics of preeclampsia and review associated risk factors.

Preeclampsia is a hypertensive disorder of pregnancy distinguished by proteinuria and/or other associated features (e.g., thrombocytopenia, acute kidney insufficiency, impaired liver function). Although parturients with preeclampsia may have peripheral edema, suggesting hypervolemia, clinically they are intravascularly hypovolemic because of the loss of oncotic pressure from proteinuria and systemic inflammation causing increased vascular permeability. Box 56.1 lists known risk factors for preeclampsia. Interestingly, maternal smoking history has shown to reduce the risk of developing preeclampsia. Patients with a history of preeclampsia and/or who have several risk factors may be given prophylactic low-dose aspirin to reduce its occurrence and/or severity when started early in pregnancy (≤ 16 weeks’ gestation).

5

What is HELLP syndrome?

HELLP ( h emolysis, e levated l iver enzymes, and l ow p latelet count) syndrome occurs in approximately 20% of patients with preeclampsia. HELLP syndrome is a microangiopathic hemolytic anemia associated with thrombocytopenia and elevated liver enzymes. The pathophysiology is complex, but is likely caused by activation of the clotting cascade, leading to a consumptive coagulopathy (thrombocytopenia), hemolysis, and liver ischemia. Symptoms may include headache, nausea/vomiting, and right upper quadrant pain secondary to liver ischemia or hepatic hemorrhage. Interestingly, around 12% of patients with HELLP syndrome may present as normotensive. Parturients who develop HELLP syndrome after 34 weeks, especially when associated with laboratory evidence of disseminated intravascular coagulation (DIC), require immediate delivery, regardless of gestational age. However, some women with HELLP syndrome are managed expectantly and may receive systemic corticosteroids for fetal lung maturity.

6

How do you differentiate HELLP syndrome from thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS)?

The pathophysiology and presentation of HELLP syndrome overlaps TTP and HUS in that they are all associated with hemolysis, transaminitis, renal injury, and thrombocytopenia. However, the primary difference is that the predominant clinical presentation of the latter two are neurological abnormalities and renal failure, respectively, whereas HELLP syndrome predominantly affects the liver and is associated with a more severe transaminitis. It is important to differentiate HELLP syndrome from other thrombotic microangiopathies, as the thrombocytopenia is usually less severe with HELLP syndrome and the mainstay of treatment is different: delivery of the fetus for HELLP syndrome and plasma exchange for TTP/HUS.

7

What is the most common cause of death in patients with preeclampsia?

Hemorrhagic stroke, followed by cardiac disease, is the leading cause of mortality in preeclampsia. The risk for stroke in preeclampsia is likely related to a combination of systemic inflammation, coagulopathy (e.g., HELLP syndrome), and uncontrolled HTN. Therefore control of blood pressure (BP) with antihypertensive agents (i.e., systolic BP < 160 mm Hg), in addition to initiating magnesium therapy (reduces cerebral edema and is neuroprotective), is of the utmost importance to minimize patient mortality. Other cause of mortality in preeclampsia are the following (in order of frequency): cardiovascular, disseminated intravascular coagulopathy, acute respiratory distress syndrome, renal failure, sepsis, and hepatic hemorrhage.