What is the initial workup for a female patient presenting with vaginal bleeding?

Initial Workup for Vaginal Bleeding in Females

The initial workup for vaginal bleeding must immediately determine pregnancy status with quantitative β-hCG testing, followed by hemodynamic assessment and transvaginal ultrasound as the primary diagnostic modality, regardless of β-hCG level. 1

Immediate Assessment (First 5 Minutes)

• Check hemodynamic stability first: Measure blood pressure, heart rate, and assess for signs of hemorrhagic shock before any other intervention 1, 2
• Obtain quantitative serum β-hCG immediately on all reproductive-age women to determine pregnancy status, as this fundamentally changes the diagnostic approach 1, 2
• Determine Rh status urgently in pregnant patients, as anti-D immunoglobulin may be needed for Rh-negative women with threatened abortion or ectopic pregnancy 1

Critical Early Diagnostic Testing

For Pregnant Patients (Positive β-hCG)

Perform transvaginal ultrasound immediately as the primary diagnostic tool, regardless of β-hCG level—never defer imaging based on low β-hCG values, as up to 36% of ectopic pregnancies present with β-hCG <1,000 mIU/mL 1. This is the most critical pitfall to avoid, as ectopic pregnancy remains the leading cause of maternal death in the first trimester and affects 13% of symptomatic ED patients 1.

Key ultrasound findings to identify:

• Intrauterine gestational sac with yolk sac or fetal pole confirms intrauterine pregnancy and essentially rules out ectopic pregnancy 1
• Absence of intrauterine pregnancy with β-hCG >2,000 mIU/mL carries 57% ectopic pregnancy risk 1
• Absence of intrauterine pregnancy with β-hCG <2,000 mIU/mL carries 28% ectopic pregnancy risk 1

For second/third trimester bleeding:

• Start with transabdominal ultrasound to screen for placenta previa, vasa previa, and placental abruption 3
• Add transvaginal ultrasound if transabdominal imaging is inconclusive or inadequate, evaluating placental location, inferior placental margin, cervical length, and vessels overlying the internal cervical os 3
• Include Duplex Doppler ultrasound to identify vasa previa (vessels overlying internal os) and distinguish fetal from maternal vessels, and to detect placental abruption by identifying areas contiguous with placenta showing no blood flow 3
• Avoid digital bimanual examination until ultrasound excludes placenta previa, as examination before imaging can precipitate catastrophic hemorrhage 1, 2

For Non-Pregnant Patients (Negative β-hCG)

• Perform speculum examination to assess for cervical lesions, polyps, inflammation, or active bleeding source 1
• Obtain transvaginal ultrasound to detect anatomic abnormalities (leiomyomas, polyps, endometrial pathology) not discernible on pelvic examination—ultrasound identifies anatomic findings in 31% of cases versus only 9% by clinical evaluation alone 4
• Evaluate endometrial thickness and appearance on ultrasound, as this predicts endometrial histology and can identify endometrial carcinoma 4

Essential Laboratory Work

• Complete blood count to assess degree of blood loss and anemia 5
• Coagulation studies (platelet count, PT, PTT, fibrinogen) if significant bleeding is present, as bleeding disorders can present as vaginal bleeding 1, 6
• For pregnancy of unknown location (indeterminate ultrasound): Arrange serial β-hCG measurements every 48 hours—normal intrauterine pregnancy shows at least 53% rise over 48 hours, though this has limited sensitivity (36%) and specificity (63%) for detecting ectopic pregnancy 1

Risk Stratification for Pregnancy of Unknown Location

When initial ultrasound shows no intrauterine or ectopic pregnancy:

• 7-20% will ultimately be ectopic pregnancies, requiring close follow-up 1
• With β-hCG <1,000 mIU/mL and indeterminate ultrasound: 15% ectopic pregnancy rate 1
• With β-hCG >1,000 mIU/mL and indeterminate ultrasound: 2% ectopic pregnancy rate 1
• Repeat ultrasound when β-hCG reaches discriminatory threshold (typically 1,500-2,000 mIU/mL), but note that ultrasound may miss up to 74% of ectopic pregnancies initially 1

Disposition and Follow-Up

• Arrange follow-up within 24-48 hours for threatened abortion with concrete plans in place before discharge 1, 2
• Continue serial β-hCG monitoring until diagnosis is established for pregnancy of unknown location—approximately 80-93% will resolve as early or failed intrauterine pregnancies 1
• Ensure hemodynamically stable patients have definitive follow-up arrangements, as delayed diagnosis of ectopic pregnancy can be fatal 1

Common Pitfalls to Avoid

• Never defer ultrasound based solely on low β-hCG levels—this is the single most dangerous error, as ectopic pregnancy can occur at any β-hCG level 1
• Do not rely on absence of risk factors to exclude ectopic pregnancy, as it can occur without traditional risk factors 1
• Avoid digital examination before ultrasound in patients beyond first trimester to prevent catastrophic hemorrhage from undiagnosed placenta previa 1, 2
• Do not assume breakthrough bleeding in oral contraceptive users is benign—33% have anatomic findings on ultrasound 4