8.2 Obstetrics: Pregnancy Complications

Obstetrics: Pregnancy Complications

Why This Matters for PANCE

Pregnancy complications are emergency scenarios heavily tested on the PANCE. You must master the diagnostic and treatment algorithms for ectopic pregnancy, the definition and medical management of preeclampsia and eclampsia, and how to differentiate causes of third-trimester bleeding.

Ectopic Pregnancy

An ectopic pregnancy is the implantation of a fertilized blastocyst outside the endometrial cavity.

• Pathophysiology and Sites: Over 95% of ectopic pregnancies occur in the fallopian tube, with the ampulla being the most common specific site, followed by the isthmus and fimbriae. Interstitial ectopics (located in the portion of the tube traversing the myometrium) are rare but carry the highest risk of catastrophic hemorrhage.
• Risk Factors: The strongest risk factor is a history of a prior ectopic pregnancy. Other significant risks include a history of pelvic inflammatory disease (PID) or salpingitis (causing tubal scarring), previous tubal surgery, assisted reproductive technology (IVF), intrauterine device (IUD) in situ, smoking, and advanced maternal age.
• Clinical Presentation: The classic triad consists of amenorrhea, unilateral pelvic or lower abdominal pain, and vaginal bleeding. In a ruptured ectopic pregnancy, patients present with sudden, severe, sharp abdominal pain, referred shoulder pain (Kehr's sign, caused by blood in the peritoneal cavity irritating the diaphragmatic phrenic nerve), syncope, and signs of hemorrhagic shock (tachycardia, hypotension, pale clammy skin, and peritoneal signs including guarding and rebound tenderness).
• Diagnostic Workup:
  • Beta-hCG Kinetics: In a normal intrauterine pregnancy (IUP), quantitative serum beta-hCG levels double approximately every 48 hours (a minimum rise of 35% is expected). In an ectopic pregnancy, levels rise slowly, plateau, or decrease.
  • Transvaginal Ultrasound (TVUS): The initial imaging study of choice. A definitive diagnosis is established if an extrauterine gestational sac with a yolk sac or embryo is visualized. An empty uterine cavity in the presence of an elevated beta-hCG is highly suspicious.
  • Discriminatory Zone: This is the threshold level of beta-hCG above which a normal intrauterine gestational sac should be visible on TVUS (usually 1,500 to 2,000 mIU/mL). If the beta-hCG is above this level and no IUP is seen, an ectopic pregnancy must be suspected.
• Management:
  • Medical Treatment (Methotrexate): A systemic folic acid antagonist that halts cell division in rapidly proliferating trophoblastic tissue.
    • Criteria for Use: Hemodynamically stable patient, beta-hCG < 5,000 mIU/mL, no fetal cardiac activity on ultrasound, adnexal mass size < 4 cm, no signs of rupture, and no contraindications (normal renal/hepatic function, no immunodeficiency, not breastfeeding, and able to comply with follow-up).
    • Monitoring: Quantitative beta-hCG is measured on days 4 and 7 after methotrexate administration. A decrease of >= 15% between days 4 and 7 is required for success. If this is not achieved, a second dose of methotrexate or surgical management is indicated.
  • Surgical Treatment: Laparoscopic salpingostomy (incising the fallopian tube to remove the ectopic tissue while preserving the tube) or laparoscopic salpingectomy (removal of the affected fallopian tube).
    • Criteria for Surgery: Hemodynamic instability, suspected or confirmed tubal rupture, beta-hCG >= 5,000 mIU/mL, fetal cardiac activity on ultrasound, adnexal mass >= 4 cm, contraindications to methotrexate, or failure of medical therapy. Salpingectomy is preferred if the tube is severely damaged or if the patient has completed childbearing.

Preeclampsia and Eclampsia

Hypertensive disorders of pregnancy occur after 20 weeks of gestation and represent a major cause of maternal and neonatal morbidity.

• Pathophysiology: The primary mechanism is abnormal remodeling of maternal spiral arteries by trophoblastic cells. Instead of transforming into large, low-resistance vessels, they remain narrow and high-resistance, leading to placental ischemia. The ischemic placenta releases anti-angiogenic factors into the maternal circulation, causing systemic endothelial dysfunction, diffuse vasospasm, and capillary leaks.
• Classifications and Criteria:
  • Gestational Hypertension: New-onset blood pressure >= 140/90 mmHg after 20 weeks gestation in a previously normotensive woman, without proteinuria or end-organ damage.
  • Preeclampsia: Blood pressure >= 140/90 mmHg after 20 weeks gestation on two readings at least 4 hours apart, PLUS new-onset proteinuria (>= 300 mg per 24-hour urine collection, or urine protein-to-creatinine ratio >= 0.3). In the absence of proteinuria, preeclampsia is diagnosed if hypertension occurs alongside any severe features:
    • Thrombocytopenia (platelets < 100,000/mcL).
    • Renal insufficiency (serum creatinine > 1.1 mg/dL or a doubling of baseline).
    • Impaired liver function (transaminases >= twice normal, or severe persistent right upper quadrant/epigastric pain).
    • Pulmonary edema.
    • New-onset cerebral or visual symptoms (severe headache unresponsive to medication, scotomas, photopsia).
  • Preeclampsia with Severe Features: Blood pressure >= 160/110 mmHg on two occasions at least 4 hours apart (or sooner if antihypertensive therapy is initiated), or any of the end-organ dysfunctions listed above.
  • Eclampsia: The onset of new generalized tonic-clonic seizures in a patient with preeclampsia, which cannot be attributed to other causes.
  • HELLP Syndrome: A severe manifestation of preeclampsia characterized by Hemolysis (schistocytes on blood smear, elevated indirect bilirubin, LDH > 600 U/L), Elevated Liver enzymes (AST/ALT), and Low Platelets (< 100,000/mcL).
• Management:
  • Seizure Prophylaxis/Treatment: Intravenous Magnesium Sulfate is the gold standard for preventing seizures in severe preeclampsia and treating active eclamptic seizures. It is continued for 24 hours postpartum.
    • Monitoring for Toxicity: Clinicians must monitor patellar reflexes, respiratory rate, and urine output. The earliest sign of toxicity is the loss of deep tendon reflexes (occurs at 8-10 mEq/L), followed by respiratory depression (at >12 mEq/L) and cardiac arrest.
    • Antidote: If toxicity occurs, stop the infusion immediately and administer 1 g of 10% Calcium Gluconate IV.
  • Hypertension Management: Administer antihypertensives for sustained blood pressures >= 160/110 mmHg to reduce the risk of maternal stroke. First-line agents are intravenous Labetalol (avoid in asthma/bradycardia), intravenous Hydralazine (can cause reflex tachycardia), or oral Nifedipine.
  • Definitive Treatment: Delivery is the only cure. For preeclampsia without severe features, delivery is at 37 weeks. For preeclampsia with severe features or eclampsia, delivery is at 34 weeks or immediately upon maternal stabilization.

Third-Trimester Vaginal Bleeding (Placenta Previa vs. Abruptio Placentae)

Differentiating the major causes of third-trimester bleeding is crucial, as their management protocols are vastly different.

• Placenta Previa: The placenta implants in the lower uterine segment, covering the internal cervical os. Risk factors include prior C-section, multiparity, and smoking. It presents as painless, bright red vaginal bleeding. A digital vaginal exam is strictly contraindicated as it can cause placental rupture and fatal hemorrhage. Perform TVUS first. Deliver via scheduled C-section at 36-37 weeks.
• Abruptio Placentae: Premature separation of a normally implanted placenta from the uterine wall. Risk factors include maternal hypertension, cocaine use, smoking, and abdominal trauma. It presents as painful, dark red vaginal bleeding with a rigid, hypertonic, and tender ("woody") uterus. It is a clinical diagnosis; ultrasound is often negative. Treatment is immediate delivery if fetal distress or maternal instability occurs.

Classic PANCE Traps & Clinical Pearls

• Keep Fingers Out: For any third-trimester bleeding, do not perform a digital exam until ultrasound rules out placenta previa.
• Normal Ultrasound in Abruption: Do not rule out placental abruption based on a normal ultrasound. Retroplacental hematomas are missed on ultrasound in over 50% of cases. Diagnosis is primarily clinical.
• Magnesium Cleared by Kidneys: Magnesium sulfate is cleared by the kidneys. In patients with renal insufficiency (creatinine > 1.1 mg/dL), the magnesium dose must be reduced and serum levels monitored closely to prevent rapid toxicity.