What is the differential diagnosis and management for an 8-week pregnant patient experiencing vaginal bleeding?

Differential Diagnosis for Vaginal Bleeding at 8 Weeks Gestation

The differential diagnosis for an 8-week pregnant patient with vaginal bleeding includes threatened abortion (most common), early pregnancy loss, ectopic pregnancy, subchorionic hematoma, gestational trophoblastic disease, and cervical lesions. 1, 2

Primary Differential Diagnoses

Most Common Presentations

• Threatened abortion (viable intrauterine pregnancy with bleeding) occurs in 7-27% of pregnancies and represents the most frequent outcome when bleeding occurs in the first trimester 1, 2
• Early pregnancy loss/spontaneous abortion carries an overall miscarriage risk of approximately 12% when first-trimester bleeding is present 1, 2, 3
• Ectopic pregnancy occurs in 7-20% of pregnancy of unknown location cases and affects 1-2% of all pregnancies, accounting for 6% of maternal deaths 2, 3, 4
• Subchorionic hematoma with viable pregnancy is a common finding on ultrasound 2, 5

Less Common but Critical Diagnoses

• Gestational trophoblastic disease is less common but must be excluded 1, 2, 6
• Cervical lesions, polyps, or cervicitis should be considered after ultrasound excludes more serious pathology 1, 2
• Uterine arteriovenous malformation can present with first-trimester bleeding, though many resolve spontaneously 5

Immediate Diagnostic Approach

Critical First Step: Imaging Before Examination

Never perform digital pelvic examination before ultrasound imaging, as this can precipitate catastrophic hemorrhage if placental abnormalities exist. 2, 5

Essential Diagnostic Tests

• Obtain transvaginal ultrasound immediately as the primary diagnostic tool, providing superior resolution compared to transabdominal ultrasound 1, 2, 5
• Quantitative beta-hCG level must be obtained regardless of ultrasound findings to help identify ectopic pregnancies and guide interpretation 1, 2, 5
• Complete blood count to assess hemoglobin if bleeding is moderate to heavy 5

Interpretation of Diagnostic Findings

Ultrasound Interpretation at 8 Weeks

• If intrauterine pregnancy with fetal cardiac activity is confirmed, ectopic pregnancy is essentially ruled out (except rare heterotopic pregnancy in <1% of spontaneous conceptions) 1, 2, 5
• If no intrauterine pregnancy is visualized, serial beta-hCG measurements every 48 hours are required until diagnosis is established 1, 2, 5
• Repeat transvaginal ultrasound when beta-hCG reaches the discriminatory threshold of 1,500-2,000 mIU/mL, above which a normal intrauterine pregnancy must show a gestational sac 1, 2, 5

Critical Diagnostic Pitfall

Ultrasound misses up to 74% of ectopic pregnancies initially, making serial beta-hCG monitoring critical when the initial ultrasound is non-diagnostic. 2, 5 Most pregnancies of unknown location (80-93%) will be early intrauterine or failed intrauterine pregnancies, but 7-20% will be ectopic, requiring vigilant follow-up 1, 2, 5

Management Based on Diagnosis

For Viable Intrauterine Pregnancy (Threatened Abortion)

• Expectant management is the treatment of choice for threatened abortion 3
• Assess for subchorionic hematoma presence if intrauterine pregnancy is confirmed 2, 5
• Schedule follow-up ultrasound in 1-2 weeks to monitor progression 1, 2, 5
• Counsel that first-trimester bleeding increases risk of preterm delivery, placental abruption, and small for gestational age infants if pregnancy continues 2, 5
• Bed rest does not improve outcomes, and there is insufficient evidence supporting the use of progestins 3

For Pregnancy of Unknown Location

• Continue serial beta-hCG measurements every 48 hours until diagnosis is established 1, 2, 5
• Gynecology referral for close monitoring is recommended 5
• Repeat ultrasound when beta-hCG reaches discriminatory zone 1, 2

For Suspected or Confirmed Ectopic Pregnancy

• Immediate specialist consultation is required 5
• Treatment options include expectant management, medical management with methotrexate, or surgical intervention based on established criteria 1, 3

For Early Pregnancy Loss

Ultrasound findings diagnostic of early pregnancy loss include a mean gestational sac diameter of 25 mm or greater with no embryo and no fetal cardiac activity when the crown-rump length is 7 mm or more. 3 Treatment options include expectant management, medical management with mifepristone and misoprostol, or uterine aspiration 3

Critical Safety Considerations

Avoiding Harm to Normal Pregnancies

Guard against overinterpretation of a single ultrasound that could lead to inappropriate treatment with methotrexate or dilation and curettage, potentially harming a normal early pregnancy. 1, 5 This harm can occur from misunderstanding the usefulness of the discriminatory level or serial values of hCG 1

Rh Status Consideration

Treatment with anti-D immune globulin is warranted for all Rh-negative patients presenting with first-trimester bleeding 7