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Common Obstetric Presentations — Study Guide

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1. Ectopic Pregnancy

Definition & Epidemiology

• Fertilized ovum implants outside the endometrial lining of the uterus
• 95% tubal, 1.5% abdominal, 0.5% ovarian, 0.03% cervical
• Responsible for >10% of all maternal deaths in the US
• Heterotopic pregnancy (concurrent intrauterine + extrauterine) risk is 1:4,000 with ART

Risk Factors

• History of pelvic inflammatory disease (PID) → 6–10× higher risk (PID scarring from N. gonorrhoeae or Chlamydia)
• Progestin-bearing IUDs, previous tubal surgery, tubal ligation
• Prior ectopic pregnancy

Classic Triad

Amenorrhea + Abdominal pain + Irregular vaginal bleeding

Diagnosis

Management

• Stable, unruptured: Methotrexate (single-dose IM) — monitor hCG until undetectable
• Ruptured / unstable: Emergency surgical intervention (salpingectomy or salpingostomy)
• Rh-negative patients: administer Rh immune globulin

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2. Preeclampsia / Eclampsia

Definition

• Mild preeclampsia: BP ≥140/90 mmHg + proteinuria >0.3 g/24 hr, after 20 weeks' gestation
• Severe preeclampsia: Systolic >160 or diastolic >110 mmHg + proteinuria >5 g/24 hr + end-organ damage
• Complicates 5–10% of all pregnancies

Risk Factors

• Nulliparity, extremes of maternal age, African American race, multiple gestation
• Pre-existing HTN, diabetes, renal disease, connective tissue disorders
• Prior or family history of preeclampsia

Pathophysiology

Severe Preeclampsia Signs & Symptoms

• Headache, visual disturbances, confusion
• RUQ/epigastric pain (hepatic involvement)
• Oliguria (<500 mL/24 hr), pulmonary edema
• Thrombocytopenia, microangiopathic hemolytic anemia
• Oligohydramnios, FGR

Management

HELLP Syndrome

• Occurs in 5–10% of preeclamptic patients
• Hemolysis + Elevated Liver enzymes + Low Platelets
• Presents with RUQ/epigastric pain, microangiopathic hemolytic anemia, ↑AST/ALT/LDH, ↓platelets
• Life-threatening emergency → prompt delivery required

Eclampsia

• Seizures or coma complicating preeclampsia
• Occurs in ~0.2% of pregnancies; maternal mortality <2% (intracranial hemorrhage is the major cause)
• Perinatal mortality 2–8.6%

Gestational Hypertension (Distinguish from Preeclampsia)

• BP ≥140/90 after 20 weeks, without proteinuria or end-organ damage
• Usually resolves within 10 days postpartum; if proteinuria develops → reclassify as preeclampsia

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3. Placenta Previa

Definition & Classification

• Incidence: ~1 in 200–250 pregnancies

Classic Presentation

Painless, bright-red vaginal bleeding in the third trimester (average first bleed at 27–32 weeks)

• Initial bleed is often self-limiting but recurs
• May present with abnormal fetal lie (transverse, breech)

Risk Factors

• Advanced maternal age, multiparity, prior cesarean section, prior placenta previa
• Uterine abnormalities, multiple gestation, tobacco use, prior abortions

Diagnosis

• Transvaginal or transabdominal ultrasound (93–98% accuracy)
• Do NOT perform digital cervical exam until previa is excluded — can precipitate severe hemorrhage
• 90% of second-trimester previas resolve by term due to "placental migration" (lower uterine segment growth)

Management

• Two large-bore IV lines, fluid resuscitation, continuous fetal monitoring
• CBC, type & crossmatch, coagulation studies (fibrinogen normal in pregnancy: 400–450 mg/dL; <300 mg/dL = significant coagulopathy)
• Central/total previa at term → cesarean delivery
• Rh-negative patients → Rh immune globulin if not given at 28 weeks

Vasa Previa (Distinguish)

• Fetal blood vessels traverse membranes over the cervical os
• Associated with velamentous cord insertion
• Fetal mortality 33–100% from exsanguination at membrane rupture
• Test blood loss for fetal hemoglobin (often insufficient time)

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4. Abruptio Placentae (Placental Abruption)

Definition

Classic Presentation

Painful vaginal bleeding + uterine tenderness + frequent contractions in third trimester

• ~80% present with vaginal bleeding
• ~66% have uterine/back pain
• ~60% have fetal distress

Pathophysiology

Risk Factors

• Hypertension (40–50% of cases)
• Cocaine use, trauma (1.5–9.4%), alcohol, tobacco
• Sudden uterine decompression (e.g., delivery of first twin), prior abruption, amniocentesis

Diagnosis

• Primarily clinical — ultrasound has high false-negative rate
• High baseline uterine pressure with contractions 1–2 min apart

Management

• Aggressive IV hydration + continuous maternal/fetal monitoring
• Labs: CBC + platelets, PT/PTT, fibrinogen, fibrin degradation products, D-dimer, type & screen, Kleihauer-Betke (fetal-maternal hemorrhage)
• DIC must be excluded
• Viable but compromised fetus → emergency cesarean delivery
• Severe/complete abruption → fetal death is inevitable without immediate delivery

Key Differentiator: Previa vs. Abruption

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5. Preterm Labor

Definition

Diagnosis

• Cervix ≥2 cm dilated or ≥80% effaced, or documented progression
• Preterm contractions without cervical change → do NOT require intervention

Risk Stratification Tools

• Cervical length (transvaginal US): short cervix = increased risk
• Fetal fibronectin (at 22–35 weeks): high negative predictive value — if negative, delivery unlikely within 7–10 days

Assessment

• Electronic FHR monitoring + contractions
• Urinalysis + culture (treat UTI)
• Sterile speculum exam if rupture of membranes suspected
• Cultures: GBS, Chlamydia, N. gonorrhoeae, HSV
• Rule out chorioamnionitis: fever, leukocytosis, uterine tenderness, fetal tachycardia

Management

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6. Premature Rupture of Membranes (PROM)

Definition

Diagnosis

• Nitrazine test: Amniotic fluid (pH >7.1) turns nitrazine paper from orange → blue (normal vaginal secretions are acidic)
• Ferning: Dried amniotic fluid forms fern-like pattern on microscopy
• 90% of patients with ruptured membranes enter spontaneous labor within 24 hrs

Risk Factors

Management by Gestational Age

Chorioamnionitis (Complication of PROM)

• Infection of chorionic/amnionic membranes; complicates 1–2% of pregnancies
• Clinical signs: Fever >38°C, maternal AND fetal tachycardia, uterine tenderness, foul amniotic fluid, ↑WBC (normal in labor up to 15,000/μL), CRP >2 mg/dL
• Treatment: IV antibiotics + delivery; regional anesthesia generally safe if patient has received antibiotics and has no signs of septicemia

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7. Postpartum Hemorrhage (PPH)

Definition

• Classic: >500 mL blood loss (vaginal delivery) or >1000 mL (cesarean)
• Clinical: Any bleeding causing hemodynamic instability
• Primary PPH: within 24 hours of delivery
• Secondary PPH: 24 hours to 6 weeks postdelivery

Causes — "4 T's"

Risk Factors for Uterine Atony

• Uterine overdistension (hydramnios, macrosomia, twins), high parity, prolonged or rapid labor, oxytocin use, intraamniotic infection, uterine-relaxing agents

Prevention

• Active management of third stage: Early oxytocin administration + early cord clamping + controlled cord traction → reduces PPH by two-thirds

Management Stepladder

1. Bimanual uterine massage + compression
2. Oxytocin 10–30 units in 1 L IV (first-line uterotonic)
3. Methylergonovine 0.2 mg IM q2–4h (contraindicated in hypertension)
4. 15-methyl PGF₂α (Hemabate) 0.25 mg IM q15–90 min (max 8 doses)
5. Surgical: Uterine curettage (retained tissue), B-Lynch suture, uterine artery ligation, emergency hysterectomy
6. Most common indications for emergency hysterectomy: Uterine atony, placenta accreta, uterine rupture

Initial Labs

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8. Gestational Diabetes Mellitus (GDM)

Epidemiology & Pathophysiology

• Affects 3–5% of pregnant women
• Pregnancy → progressive insulin resistance (driven by human placental lactogen ↑ with gestational age)
• Most women compensate; a subset cannot

High-Risk Groups

Fetal Complications

Screening Protocol

• Fasting ≥95 | 1 hr ≥180 | 2 hr ≥155 | 3 hr ≥140 mg/dL

Management

1. Diet: 30–35 kcal/kg lean body weight/day + exercise (walking)
2. Monitor fasting (<105 mg/dL) and 2-hr postprandial (<120 mg/dL) blood sugars
3. If targets not met → insulin therapy
4. Ultrasound for fetal size q4–6 weeks; antenatal testing in third trimester if insulin-requiring

Long-Term Risk

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Quick Reference: Third-Trimester Bleeding Differential

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Key Drug Summary

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