What is an arcuate uterus?

Arcuate Uterus: Definition and Clinical Significance

An arcuate uterus is a minor uterine anomaly characterized by a slight indentation or concavity of the uterine fundus that projects into the endometrial cavity, typically with a fundal indentation less than 1 cm deep. This represents one of the mildest forms of congenital uterine malformations.

Diagnostic Criteria and Imaging

The diagnosis of arcuate uterus is typically made through imaging studies:

• Transvaginal ultrasound (TVUS) is the first-line imaging modality for evaluation, especially when combined with 3D capabilities 1
• MRI provides excellent accuracy (100% in studies) for classifying Müllerian duct anomalies 1
• Key diagnostic features include:
  • Fundal indentation <1 cm (compared to >1 cm in bicornuate uterus) 1
  • Smooth, concave contour of the uterine fundus projecting into the endometrial cavity
  • Normal external uterine contour

Three-dimensional ultrasound has significantly improved the accuracy of diagnosing arcuate uterus, with similar accuracy to MRI for detecting Müllerian anomalies 1.

Clinical Significance and Reproductive Outcomes

The clinical significance of arcuate uterus has been debated in the literature:

• Pregnancy rates: Arcuate uterus does not appear to reduce fertility or pregnancy rates following assisted reproductive technology (ART) 2

• Miscarriage risk:

  • Increased risk of second-trimester miscarriage (RR 2.39) compared to normal uteri 3
  • First-trimester miscarriage rates appear similar to those with normal uteri (13.9% vs 12.7%) 2

• Perinatal complications: According to the most recent evidence (2025), arcuate uterus is associated with:

  • Higher rates of preterm delivery (13% vs 4.7%, adjusted OR 4.0) 4
  • Increased fetal growth restriction (16% vs 6.7%, adjusted OR 2.6) 4
  • Higher incidence of abnormal placental cord insertion (33% vs 7.6%, adjusted OR 6.0) 4

• Fetal malpresentation: Significantly increased risk (RR 2.53) compared to normal uteri 3

Differentiation from Other Uterine Anomalies

Arcuate uterus must be distinguished from more severe uterine anomalies:

• Septate/subseptate uterus: Has a deeper indentation (≥1.5 cm) and may have more significant reproductive implications 5
• Bicornuate uterus: Shows external fundal cleft >1 cm and fundal indentation >5 mm above the interostial line 1

Management Considerations

Management should be guided by clinical presentation:

• Asymptomatic patients: Generally no intervention required
• Recurrent pregnancy loss: Some evidence suggests that surgical correction (hysteroscopic metroplasty) may improve outcomes in selected cases, though this remains controversial 5
• Pregnancy monitoring: Given the increased risks of preterm delivery, fetal growth restriction, and abnormal placental cord insertion, closer monitoring during pregnancy may be warranted 4

Important Considerations

• The distinction between arcuate and subseptate uterus has been questioned, as some studies show similar reproductive outcomes before and after surgical correction 5
• The most recent evidence (2025) suggests that even this "minor" uterine anomaly may have significant implications for perinatal outcomes 4
• Accurate diagnosis using 3D imaging techniques is essential for proper classification and management planning

Understanding the specific characteristics and potential complications associated with arcuate uterus allows for appropriate counseling and management of affected individuals, particularly during pregnancy.