A 25-year-old pregnant woman at 28 weeks gestation presents with a headache. Her pregnancy has been managed by a nurse practitioner. Her temperature is 99.0°F (37.2°C), blood pressure is 164/104 mmHg, pulse is 100/min, respirations are 22/min, and oxygen saturation is 98% on room air. Physical exam is notable for a comfortable appearing woman with a gravid uterus. Laboratory tests are ordered as seen below. Hemoglobin: 12 g/dL Hematocrit: 36% Leukocyte count: 6,700/mm^3 with normal differential Platelet count: 100,500/mm^3 Serum: Na+: 141 mEq/L Cl-: 101 mEq/L K+: 4.4 mEq/L HCO3-: 25 mEq/L BUN: 21 mg/dL Glucose: 99 mg/dL Creatinine: 1.0 mg/dL AST: 32 U/L ALT: 30 U/L Urine: Color: Amber Protein: Positive Blood: Negative Which of the following is the most likely diagnosis?

Acute fatty liver disease of pregnancy

A 25-year-old primigravida woman at 35 weeks estimated gestational age presents with a headache for the past 5 hours. She describes the headache as severe and incapacitating and showing no response to acetaminophen. In the emergency department, her blood pressure is found to be 150/100 mm Hg, pulse is 88/min, respiratory rate is 30/min, and temperature is 37.0°C (98.6°F). Her records show that her blood pressure was the same yesterday during her regular antenatal visit. Chest auscultation reveals bilateral crackles along the lung base. Abdominal examination reveals a gravid uterus consistent with a gestational age of 32 weeks and a floating fetus in a cephalic presentation. Pelvic examination is performed which shows a closed firm cervix with no evidence of bleeding or discharge. Moderate pitting edema is noted and neurologic examination shows generalized hyperreflexia. Laboratory findings are significant for the following: Hemoglobin 12.5 g/dL Platelets 185,000/μL Serum creatinine 0.4 mg/dL Spot urine creatinine 110 mg/dL Spot urine protein 360 mg/dL AST 40 IU/L Which of the following is the most likely diagnosis in this patient?

Preeclampsia with severe features

Preeclampsia without severe features

A 29-year-old woman presents to a medical office complaining of fatigue, nausea, and vomiting for 1 week. Recently, the smell of certain foods makes her nauseous. Her symptoms are more pronounced in the mornings. The emesis is clear-to-yellow without blood. She has had no recent travel out of the country. The medical history is significant for peptic ulcer, for which she takes pantoprazole. The blood pressure is 100/60 mm Hg, the pulse is 70/min, and the respiratory rate is 12/min. The physical examination reveals pale mucosa and conjunctiva, and bilateral breast tenderness. The LMP was 9 weeks ago. What is the most appropriate next step in the management of this patient?

Beta-HCG levels and a transvaginal ultrasound

Beta-HCG levels and a transabdominal ultrasound

Beta-HCG levels and a pelvic CT

A previously healthy 29-year-old Taiwanese woman comes to the emergency department with vaginal bleeding and pelvic pressure for several hours. Over the past 2 weeks, she had intermittent nausea and vomiting. A home urine pregnancy test was positive 10 weeks ago. She has had no prenatal care. Her pulse is 80/min and blood pressure is 150/98 mm Hg. Physical examination shows warm and moist skin. Lungs are clear to auscultation bilaterally. Her abdomen is soft and non-distended. Bimanual examination shows a uterus palpated at the level of the umbilicus. Her serum beta human chorionic gonadotropin concentration is 110,000 mIU/mL. Urine dipstick is positive for protein and ketones. Transvaginal ultrasound shows a central intrauterine mass with hypoechoic spaces; there is no detectable fetal heart rate. An x-ray of the chest shows no abnormalities. Which of the following is the most appropriate next step in management?

Bed rest and doxylamine therapy

Red flags in pregnancy for USMLE Step 3: High-Yield Diagnosis Lessons

Red flags in pregnancy - First Trimester Alarms

Ectopic Pregnancy: Unilateral pelvic pain, amenorrhea, and vaginal bleeding.
- ⚠️ Watch for hCG levels that fail to double every 48-72 hours.
- Signs of rupture: severe pain, shoulder tip pain (phrenic nerve irritation), hemodynamic instability.
Molar Pregnancy (Gestational Trophoblastic Disease):
- Vaginal bleeding ("prune juice" discharge), uterine size > dates, hyperemesis.
- Markedly ↑ hCG levels (often >100,000 mIU/mL).
- Ultrasound: "snowstorm" appearance.
Hyperemesis Gravidarum: Severe, persistent nausea/vomiting leading to:
- Weight loss >5% of pre-pregnancy body weight.
- Ketonuria and electrolyte abnormalities (e.g., hypokalemia).

⭐ An empty uterus on transvaginal ultrasound with a serum hCG level above the discriminatory zone (1,500-2,000 mIU/mL) is highly suggestive of an ectopic pregnancy.

Red flags in pregnancy - Later Gestation Alerts

Severe, persistent headache, visual changes (scotomata), or RUQ pain
- Suggests pre-eclampsia with severe features.
- Check BP: new onset hypertension (>140/90 mmHg) after 20 weeks is a key sign.
Vaginal Bleeding
- Painful bleeding with uterine tenderness/rigidity: suspect Placental Abruption.
- Painless, bright red bleeding: suspect Placenta Previa.
- ⚠️ Never perform a digital vaginal exam in cases of third-trimester bleeding until placenta previa is ruled out by ultrasound.
Decreased Fetal Movement
- Maternal perception of significantly reduced or absent fetal activity.
- Requires immediate assessment with a Non-Stress Test (NST) or Biophysical Profile (BPP).
Gush of Fluid from Vagina
- Suggests Preterm Premature Rupture of Membranes (PPROM) if < 37 weeks.
- Increases risk for chorioamnionitis and preterm labor.

⭐ In placental abruption, the bleeding is maternal blood from the decidua basalis. In vasa previa, the bleeding is fetal blood, leading to rapid fetal exsanguination and distress.

Red flags in pregnancy - Fetal & Systemic Signs

Fetal Signs:
- ↓ Fetal movement (kick counts < 10 in 2 hours).
- Absent fetal heart tones > 12 weeks by Doppler.
- Fetal heart rate (FHR) abnormalities: < 110 or > 160 bpm; late decelerations.
Maternal Systemic Signs:
- BP ≥ 160/110 mmHg.
- Severe headache, visual changes (scotomata).
- Epigastric/RUQ pain (→ HELLP).
- Seizures (→ Eclampsia).
- Vaginal bleeding, esp. with pain.
- Fever > 38°C (100.4°F).

⭐ A sudden gush of fluid from the vagina suggests premature rupture of membranes (PROM), a key risk for infection and preterm labor.

Fetal Heart Rate Decelerations: Early, Late, Variable

High-Yield Points - ⚡ Biggest Takeaways

Severe headache, visual disturbances, or epigastric pain suggest preeclampsia.

Vaginal bleeding requires immediate evaluation for placenta previa or abruption.

A sudden gush of fluid indicates possible preterm premature rupture of membranes (PPROM).

Decreased or absent fetal movement is a critical sign of potential fetal distress.

Unilateral leg swelling or sudden dyspnea raises concern for thromboembolism (DVT/PE).

Fever and uterine tenderness may signal chorioamnionitis.

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Red flags in pregnancy