What is the differential diagnosis for an 8-week pregnant patient presenting with vaginal bleeding?

Differential Diagnosis for Vaginal Bleeding at 8 Weeks Gestation

The primary differential diagnoses to consider are threatened abortion (most common, occurring in 7-27% of pregnancies), early pregnancy loss (12% miscarriage risk with first trimester bleeding), ectopic pregnancy (7-20% of pregnancy of unknown location cases), subchorionic hematoma, gestational trophoblastic disease, and cervical lesions. 1

Immediate Diagnostic Workup

Obtain transvaginal ultrasound immediately as the first diagnostic step—never perform digital pelvic examination before imaging, as this can precipitate catastrophic hemorrhage if placental abnormalities exist. 1, 2

• Transvaginal ultrasound provides superior resolution compared to transabdominal approach and is the cornerstone of evaluation 1, 2
• Obtain quantitative beta-hCG level simultaneously, regardless of ultrasound findings, to help identify ectopic pregnancies and guide interpretation 1, 2
• Complete blood count if bleeding is moderate to heavy 2

Primary Differential Diagnoses

Threatened Abortion (Most Common)

• Represents viable intrauterine pregnancy with bleeding, occurring in 7-27% of pregnancies 1
• Most frequent outcome when bleeding occurs in first trimester 1

Early Pregnancy Loss

• Overall miscarriage risk approximately 12% when first-trimester bleeding is present 1
• Ultrasound findings diagnostic of early pregnancy loss include mean gestational sac diameter ≥25 mm with no embryo, or no fetal cardiac activity when crown-rump length is ≥7 mm 3

Ectopic Pregnancy (Most Critical to Exclude)

• Occurs in 7-20% of pregnancy of unknown location cases and affects 1-2% of all pregnancies 1
• Accounts for 6% of maternal deaths, making this the most critical diagnosis to exclude 1, 4
• Ultrasound initially misses up to 74% of ectopic pregnancies, making serial beta-hCG monitoring absolutely critical when initial ultrasound is non-diagnostic 2

Subchorionic Hematoma

• Should be assessed if intrauterine pregnancy is confirmed on ultrasound 1, 2
• Requires follow-up ultrasound in 1-2 weeks 2

Gestational Trophoblastic Disease

• Less common but important to exclude 2
• Doppler ultrasound may be helpful as ancillary tool 2

Cervical Lesions, Polyps, or Cervicitis

• Identified after ultrasound excludes more serious pathology 2
• Assessed during speculum examination for cervical lesions, polyps, or inflammation 5

Interpretation of Ultrasound Findings

If Intrauterine Pregnancy with Fetal Cardiac Activity Confirmed:

• Ectopic pregnancy is essentially ruled out (except rare heterotopic pregnancy in <1% of spontaneous conceptions) 1, 2
• Assess for subchorionic hematoma presence 1, 2
• Schedule follow-up ultrasound in 1-2 weeks to monitor progression 2
• Counsel that first trimester bleeding increases risk of preterm delivery, placental abruption, and small for gestational age infants 2

If No Intrauterine Pregnancy Visualized:

• Serial beta-hCG measurements every 48 hours are required until diagnosis is established 1, 2
• Repeat transvaginal ultrasound when beta-hCG reaches discriminatory threshold of 1,500-2,000 mIU/mL 6, 2
• 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 2

Management Based on Diagnosis

Viable Intrauterine Pregnancy (Threatened Abortion):

• Expectant management is recommended 3
• Bed rest does not improve outcomes 3
• Follow-up ultrasound in 1-2 weeks 2

Pregnancy of Unknown Location:

• Continue serial beta-hCG measurements every 48 hours until diagnosis established 1, 2
• Gynecology referral for close monitoring 2

Suspected or Confirmed Ectopic Pregnancy:

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

Early Pregnancy Loss:

• Treatment options include expectant management, medical management with mifepristone and misoprostol, or uterine aspiration 3
• Urgent obstetric consultation is necessary 4

Critical Pitfalls to Avoid

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, 2

• Never perform digital pelvic examination before ultrasound imaging 2
• Remember that ultrasound misses up to 74% of ectopic pregnancies initially 2
• Serial beta-hCG monitoring is critical when initial ultrasound is non-diagnostic 2
• Speculum examination is indicated only in those presenting with severe bleeding or hypotension, as removal of obstructing endocervical products can be a crucial resuscitative measure 7

Additional Considerations

• Treat all Rh-negative patients with anti-D immune globulin 4
• Assess for rare diagnoses including uterine arteriovenous malformation if bleeding pattern is atypical 2