What is a threatened abortion?

Threatened Abortion: Definition, Diagnosis, and Management

A threatened abortion is defined as vaginal bleeding with or without uterine cramping during the first half of pregnancy while the cervix remains closed and the pregnancy is still viable. 1 This condition may progress to spontaneous abortion (miscarriage) but often continues to term with or without treatment.

Clinical Presentation and Diagnosis

• Symptoms and Signs:

  • Vaginal bleeding (usually light to moderate)
  • Mild uterine cramping/pain
  • Closed cervical os on examination
  • Viable pregnancy with detectable fetal cardiac activity

• Diagnostic Criteria:

  • Transvaginal ultrasound showing:
    • Intrauterine gestational sac
    • Presence of embryo with cardiac activity
    • Possible subchorionic hematoma (blood collection between gestational sac and uterine wall)
  • Closed cervical os on speculum examination
  • Positive pregnancy test (serum or urine hCG)

Prognosis

• Approximately 75-80% of threatened abortions continue to term 2
• Spontaneous abortion occurs in less than 30% of cases 2
• Risk factors for progression to complete abortion include:
  • Larger subchorionic hematoma (>20 cm²) 2
  • Increasing maternal age
  • History of previous miscarriages
  • Heavy bleeding or severe pain

Complications and Associated Risks

Women with threatened abortion who continue their pregnancy have increased risk of:

• Preterm labor (25.2% vs 9.4% in women without threatened abortion) 3
• Premature rupture of membranes (10.2% vs 4.8%) 3
• Placental abruption (4% vs 1.4%) 3
• Lower birth weight at term 3
• Intrauterine growth restriction (13.2%) 2
• Antepartum hemorrhage (7.5%) 2
• Intrauterine fetal death (5.66%) 2

Management Approach

1. Initial Assessment:

   • Confirm intrauterine pregnancy with ultrasound
   • Verify fetal cardiac activity
   • Rule out ectopic pregnancy
   • Assess amount of bleeding and hemodynamic stability

2. Treatment Options:

   • Bed rest: Though traditionally recommended, limited evidence supports its effectiveness
   • Progesterone supplementation: May be beneficial in cases of luteal phase deficiency
   • Folic acid supplementation: Recommended for all pregnant women
   • Avoid digital cervical examinations: These may increase risk of infection 4

3. Rh Status Management:

   • For Rh-negative women with threatened abortion, administration of anti-D immunoglobulin (50 μg) is controversial
   • British authorities suggest anti-D may be unnecessary before 12 weeks if the pregnancy continues 1
   • However, it may be prudent to administer anti-D when there is "heavy" bleeding, associated abdominal pain, or when the event occurs near 12 weeks' gestation 1
   • ACOG notes there is no evidence-based recommendation, and many physicians do not treat when there is a live embryo or fetus 1

4. Follow-up Care:

   • Serial ultrasounds to monitor fetal viability and growth
   • Monitor for resolution of bleeding
   • Increased antenatal surveillance for complications

Patient Counseling

• Explain the condition and its prognosis
• Advise to report increased bleeding, severe pain, or passage of tissue
• Discuss warning signs requiring immediate medical attention:
  • Heavy bleeding (soaking through a pad in less than an hour)
  • Severe abdominal pain
  • Fever or chills
  • Foul-smelling vaginal discharge
• Address psychological impact and provide emotional support

Important Distinctions

Threatened abortion must be distinguished from other types of early pregnancy loss:

• Inevitable abortion: Cervical dilation with bleeding and cramping
• Incomplete abortion: Partial expulsion of products of conception
• Complete abortion: Complete expulsion of all products of conception
• Missed abortion: Non-viable pregnancy with no expulsion of products
• Septic abortion: Infection of the products of conception

Common Pitfalls to Avoid

1. Failure to confirm intrauterine pregnancy: Always rule out ectopic pregnancy
2. Unnecessary cervical examinations: Digital examinations should be avoided to prevent infection
3. Overtreatment: Most threatened abortions with viable fetuses will continue without intervention
4. Inadequate follow-up: Patients require close monitoring for potential complications
5. Neglecting psychological support: Patients often experience significant anxiety and fear of pregnancy loss

By understanding the definition, diagnosis, and management of threatened abortion, clinicians can provide appropriate care and counseling to patients experiencing this common complication of early pregnancy.