What should a pregnant woman do if she experiences spotting during her first trimester?

Management of First Trimester Spotting

If you experience spotting during the first trimester, obtain a transvaginal ultrasound combined with quantitative beta-hCG level immediately, before any digital pelvic examination is performed. 1, 2

Immediate Diagnostic Workup

Essential Initial Testing

• Transvaginal ultrasound is the primary diagnostic tool and provides superior resolution compared to transabdominal ultrasound for evaluating early pregnancy structures, fetal cardiac activity, and potential complications like subchorionic hematoma 1, 2
• Quantitative beta-hCG level must be obtained regardless of ultrasound findings to help identify ectopic pregnancies and guide interpretation, with a discriminatory threshold of 1,500-2,000 mIU/mL for detecting intrauterine pregnancy 1, 3
• Blood type and screen should be obtained if not already on file, particularly to identify Rh-negative patients who will need anti-D immunoglobulin to prevent alloimmunization 1
• Complete blood count should be obtained if bleeding is moderate to heavy to assess hemoglobin levels and detect potential anemia 1

Critical Safety Consideration

• Never perform digital pelvic examination before ultrasound imaging, as this can precipitate catastrophic hemorrhage if placental abnormalities exist 2, 3

Interpretation of Results and Next Steps

If Intrauterine Pregnancy with Fetal Cardiac Activity is Confirmed

• Ectopic pregnancy is essentially ruled out (except in rare cases of heterotopic pregnancy occurring in <1% of spontaneous conceptions) 1, 2
• Schedule follow-up ultrasound in 1-2 weeks to monitor progression 1, 2
• Counsel about increased risks: first trimester bleeding is associated with increased risk of preterm delivery, placental abruption, and small for gestational age infants 2, 3
• Consider oral iron supplementation if hemoglobin drops significantly 1, 3
• Assess for subchorionic hematoma and document its location relative to the placenta 1

If No Intrauterine Pregnancy is Visualized (Pregnancy of Unknown Location)

• Serial beta-hCG measurements every 48 hours should be obtained until diagnosis is established 1, 2, 3
• Repeat transvaginal ultrasound when beta-hCG reaches discriminatory threshold of 1,500-2,000 mIU/mL 1, 3
• Refer to gynecology for close monitoring, as 7-20% of pregnancies of unknown location will be ectopic pregnancies 1, 2, 3
• Most pregnancies of unknown location (80-93%) will be early intrauterine or failed intrauterine pregnancies, but vigilant follow-up is critical 2, 3

If Ectopic Pregnancy is Suspected or Confirmed

• Immediate specialist consultation is required 1, 2

Common Differential Diagnoses

The most common causes of first trimester spotting include:

• Threatened abortion (viable intrauterine pregnancy with bleeding), occurring in 7-27% of pregnancies 1, 2
• Early pregnancy loss/spontaneous abortion, with approximately 12% overall miscarriage risk with first trimester bleeding 1, 2
• Subchorionic hematoma with viable pregnancy, occurring in 7-27% of cases 1
• Ectopic pregnancy, occurring in 7-20% of pregnancy of unknown location cases 1, 2

Special Considerations for Rh-Negative Patients

• Rh-negative patients with vaginal bleeding should receive anti-D immunoglobulin to prevent alloimmunization 1

Critical Pitfalls to Avoid

• Ultrasound misses up to 74% of ectopic pregnancies initially, making serial beta-hCG monitoring critical when initial ultrasound is non-diagnostic 2, 3
• Avoid overinterpretation of a single ultrasound that could lead to inappropriate treatment with methotrexate or dilation and curettage, potentially harming a normal early pregnancy 2
• Doppler ultrasound should be avoided in first trimester due to potential bioeffects on the developing embryo; embryonic cardiac activity should be documented using M-mode ultrasound or video clips instead 1