Physiologic Adaptations & Hypertension in Pregnancy

Physiologic adaptations in normal pregnancy

• Blood volume increases by approximately 40% during pregnancy.
• Platelet count can drop below 200 x 10^9/L due to increased blood volume.
• Coagulation factors like fibrinogen and factor VII increase.
• Marked generalized vasodilation occurs, decreasing peripheral resistance.
• Arterial resistance reduces in response to angiotensin II.
• Cardiac output and stroke volume increase.
• Mean arterial pressure decreases by 10 mm Hg.
• Increased renal blood flow and glomerular filtration rate (by 50%) due to vasodilation.
• Creatinine clearance increases, while serum creatinine and urea decrease.
• Increased uric acid clearance and calcium excretion.
• Glucosuria and aminoaciduria are present.
• Endocrine changes occur, including changes in parathyroid, adrenal, weight, and gastrointestinal function.

Hypertension in Pregnancy

• Sustained elevated blood pressure at rest, measured on two occasions at least 6 hours apart.
• Prevalence: 10% of all pregnancies.

Classification

• Pre-eclampsia
• Chronic hypertension (HTN)
• Transient HTN (Gestational HTN)

Pre-eclampsia

• Defined as sustained hypertension with proteinuria and edema (edema not essential for diagnosis).
• Onset occurs after 20 weeks of gestation.
• Accounts for 50% of all hypertension in pregnancies.
• Usually resolves postpartum.

Mild pre-eclampsia

• Most common type, often asymptomatic.
• Characterized by:
  • Blood pressure ≥ 140/90 mm Hg or an increase in systolic BP by 30 mm Hg or diastolic BP by 15 mm Hg above non-pregnant baseline.
  • Proteinuria (1-2+ on dipstick or > 300 mg/24 hr).
  • Edema (non-dependent, hands and face, often associated with excessive weight gain).

Severe pre-eclampsia

• Less common.
• Can be diagnosed based on:
  • Severe hypertension (BP ≥ 160/110 mm Hg).
  • Severe proteinuria (3-4+ on dipstick or > 5 g/24 hr) alone without symptoms.
  • Mild hypertension and proteinuria if signs and symptoms are present:
    • Pulmonary edema
    • Cyanosis
    • Congestive cardiac failure (CCF)
    • Increased serum creatinine, oliguria
    • Elevated liver function tests (LFTs), right upper quadrant (RUQ) or epigastric pain
    • Visual disturbances (e.g., scotomas, loss of peripheral vision), headache, convulsions
    • Severe nausea and vomiting
    • Thrombocytopenia, microangiopathic hemolysis

HELLP Syndrome

• A type of severe pre-eclampsia.
• Hemolysis, Elevated Liver enzymes, Low Platelets.

Eclampsia

• Latin for convulsions.
• Unexplained tonic-clonic seizures with mild or severe pre-eclampsia.
• Most commonly occurs intrapartum (50%), but can also occur antepartum and postpartum.

Chronic HTN

• Patient may have any underlying disease causing HTN, such as:
  • Essential HTN
  • Arteriosclerosis and chronic glomerulonephritis
  • Chronic pyelonephritis
  • Systemic lupus erythematosus (SLE)

Uncomplicated Chronic HTN

• Pre-existing HTN
• HTN diagnosed ≤ 20 weeks' gestation.
• HTN persisting ≥ 6 weeks postpartum.
• Not induced by pregnancy.

Complicated Chronic HTN (Superimposed preeclampsia)

• Isolated hypertension without proteinuria.
• Characterized by:
  • Worsening hypertension ± proteinuria
  • Symptoms of severe pre-eclampsia late in pregnancy.

Transient HTN

• Late HTN (Gestational HTN).
• Non-sustained (transient) increase in blood pressure without proteinuria or symptoms in the latter half of pregnancy.
• No impact on pregnancy outcome.

Risk Factors

• Maternal Factors

  • Demographic criteria:
    • Primipara (first pregnancy) is the most common risk factor.
    • Age extremes (≤ 18 years or ≥ 34 years).
  • Medical complications:
    • Diabetes mellitus (DM)
    • Chronic HTN
    • Pre-existing renal disease
    • SLE
  • Past or family history (FHx) of pregnancy-induced hypertension.

• Fetal Factors

  • Hydatidiform mole

  • 1 fetus

  • Fetal hydrops
  • Intrauterine growth restriction (IUGR)

Explore the key physiologic adaptations that occur during normal pregnancy, including changes in blood volume, cardiac output, and renal function. Delve into the aspects of hypertension that can emerge during this critical time, including diagnosis and prevalence. This quiz will help reinforce your understanding of maternal physiological changes and their implications.