In-Depth Study Notes on Pregnancy and Preterm Labor

Physiology of Pregnancy

  • Changes in drug action during pregnancy

  • Increased effect of circulating steroid hormones affects liver drug metabolism.

  • Reduced gastrointestinal (GI) motility and increased gastric pH alters drug absorption.

  • Increased glomerular filtration rate (GFR) and renal perfusion affect drug elimination.

  • Expanded maternal blood volume leads to greater drug dilution.

  • Altered drug clearance during late pregnancy may decrease drug concentrations.

  • Factors that alter drug half-lives

  • Pregnancy itself

  • Labor processes

  • Certain disease states

  • Teratogens, which cause developmental abnormalities.

Therapeutic Drugs and Use of Herbs in Pregnancy

  • Iron

  • Common adverse reactions:

    • Nausea, vomiting, constipation
    • Black tarry stools, diarrhea
    • Epigastric pain, urine discoloration.

  • Nursing implications:

    • Educate patients to dilute liquid iron and use a straw to avoid teeth discoloration.
    • Administer on an empty stomach with water or juice; vitamin C enhances absorption.

  • Possible gastric upset; can be taken with food if necessary.

  • Avoid antacids, eggs, milk, coffee, tea, and cereal to improve absorption.

  • Folic Acid (B9, Folate)

  • Foods high in folic acid include:

    • Dark green leafy vegetables (e.g., spinach, kale)
    • Asparagus, papayas, strawberries, oranges.

  • Enriched foods include bread, rice, pasta, cornmeal, and cereal.

  • Adverse reactions include:

    • Bronchospasm, rash, malaise, intense yellow urine.

  • Routine multi-vitamin use is recommended for pregnant women.

Drugs for Minor Discomforts of Pregnancy

  • Nausea and Vomiting:

  • Non-pharmacologic measures recommended.

  • Medications include:

    • Pyridoxine hydrochloride
    • Doxylamine succinate.

  • Heartburn:

  • Non-pharmacologic measures; can use:

    • Antacids, chewable calcium carbonate
    • Histamine2 receptor antagonists and proton pump inhibitors.

  • Constipation:

  • Non-pharmacologic measures; consider bulk-forming preparations and docusate sodium.

  • Occasional use of:

    • Magnesium hydroxide, magnesium citrate, lactulose, sorbitol, bisacodyl, senna.

  • Pain Management:

  • Non-pharmacologic measures; acetaminophen is safe.

  • Avoid aspirin in pregnancy; ibuprofen is contraindicated in the third trimester.

  • Antidepressant Drugs:

  • SSRIs and TCAs may cause adverse birth outcomes:

    • Low birthweight, decreased attentiveness, irritability in neonates.

Drugs That Decrease Uterine Muscle Contractility

  • Preterm Labor:

  • Tocolytic therapy (off-label use) options include:

    • Beta2 sympathomimetics (e.g., Terbutaline)
    • Calcium antagonists and magnesium sulfate.

  • Terbutaline (Beta-sympathomimetic):

  • Mechanism: Stimulates beta2-receptors on uterine smooth muscle to reduce contractions.

  • Adverse reactions:

    • Tremors, dizziness, palpitations, tachycardia, hypotension.

  • Magnesium Sulfate (Calcium antagonist):

  • Mechanism: Relaxes uterine smooth muscle via calcium displacement.

  • Adverse reactions:

    • Flushing, dizziness, respiratory depression, potential for cardiac arrest.

Nursing Interventions During Tocolytic Therapy

  • Monitor maternal and fetal status:
  • Daily weight, intake/output, and vital signs.
  • Assess for uterine contractions and pain.
  • Monitor serum magnesium levels (therapeutic range: 4-7 mg/dL).
  • Keep calcium gluconate (1g IV) on hand as antidote for magnesium toxicity.
  • Assess newborn for effects of magnesium post-delivery.

Corticosteroid Therapy in Preterm Labor

  • Medications: Betamethasone, Dexamethasone

  • Actions include accelerating lung maturation and surfactant development in the fetus, reducing respiratory distress syndrome incidence.

  • Adverse reactions for Betamethasone and Dexamethasone include seizures, bradycardia, insomnia, and hypersensitivity.

  • Clinical Judgment:

  • Ensure proper administration techniques, including shaking the suspension and monitoring maternal vitals.

Drugs for Gestational Hypertension

  • Common complications:

  • Preeclampsia: Gestational hypertension with proteinuria.

  • Severe forms lead to HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelet count).

  • Treatment Options:

  • Methyldopa for mild preeclampsia.

  • Hydralazine for severe preeclampsia.

  • Magnesium Sulfate for seizure prevention.

  • Adverse reactions for treatments:

  • Methyldopa: Edema, anxiety, and drowsiness.

  • Hydralazine: Tachycardia, hypotension, and nausea.

  • Magnesium sulfate: Lethargy, hypotension, and need for calcium gluconate as antidote (1g IV).