What is the association between breech presentation and trigonocephaly, and what are the recommended evaluation and management steps?

Association Between Breech Presentation and Trigonocephaly

Breech presentation is significantly associated with trigonocephaly (metopic craniosynostosis), occurring in approximately 10% of trigonocephaly cases compared to 4% in the general population, representing a 2.5-fold increased risk. 1

Epidemiological Evidence

The strongest evidence comes from a large international multicentre retrospective cohort study examining 152 trigonocephaly patients, which demonstrated:

• Breech position occurs in 10% of trigonocephaly patients versus 4% in controls (p = 0.003) 1
• Trigonocephaly patients also show higher rates of preterm birth (11% vs 6%, p < 0.001) 1
• Assisted reproductive technology is more common in trigonocephaly cases (13% vs 3%, p < 0.001) 1
• Labor induction rates are significantly elevated in trigonocephaly patients 1
• Cesarean section rates are markedly higher in this population 1

Bidirectional Relationship

The association appears bidirectional:

• Breech presentation serves as a marker for congenital anomalies, including craniosynostosis - infants delivered breech have 11.7% prevalence of at least one congenital anomaly versus 5.1% in cephalic presentations 2
• Among full-term breech infants specifically, the anomaly rate is 9.4% versus 4.6% in cephalic presentations (adjusted OR 2.09,95% CI 1.96-2.23) 2
• Craniosynostosis may mechanically impair fetal head molding, contributing to persistent breech positioning and delivery complications 1

Proposed Mechanisms

Several pathophysiologic explanations exist for this association:

• Impaired fetal head molding - the prematurely fused metopic suture prevents normal skull deformation needed for spontaneous version and vaginal delivery 1
• Altered intrauterine positioning dynamics - breech fetuses demonstrate less pronounced development of lateralized head-position preference compared to cephalic fetuses, particularly after 36 weeks gestation 3
• Shared risk factors - both conditions associate with assisted reproductive technology, suggesting possible common etiologic pathways 4, 1

Clinical Evaluation Recommendations

When trigonocephaly is identified or suspected:

• Document fetal presentation at each prenatal visit starting at 28 weeks gestation 1
• Perform detailed anatomic ultrasound to assess for additional congenital anomalies, as breech presentation increases overall malformation risk 2
• Evaluate skull morphology specifically - look for the characteristic triangular forehead shape, midline frontal ridge, and hypotelorism on prenatal imaging 1
• Obtain detailed obstetric history including method of conception, as ART increases trigonocephaly risk 4-fold 1

When breech presentation persists at term:

• Conduct thorough postnatal examination for craniosynostosis and other anomalies, as breech delivery is a significant marker for congenital defects 2
• Examine head shape carefully - palpate for ridging along the metopic suture and assess for frontal narrowing 1
• Maintain low threshold for pediatric neurosurgery referral if any cranial dysmorphology is detected 1

Management Implications

The association impacts delivery planning:

• External cephalic version may have lower success rates in fetuses with craniosynostosis due to impaired head molding, though this has not been specifically studied 1, 5
• Cesarean section rates are inherently higher in trigonocephaly patients (specific rate not quantified but statistically significant) 1
• Prenatal detection of craniosynostosis could improve perinatal care planning by allowing preparation for potential delivery complications 1

Critical Pitfalls to Avoid

• Do not dismiss persistent breech presentation as merely positional - it warrants evaluation for underlying structural anomalies including craniosynostosis 1, 2
• Avoid assuming isolated breech presentation - actively search for associated malformations, as 11.7% of breech infants have at least one congenital anomaly 2
• Do not delay postnatal cranial assessment in breech-delivered infants, as early surgical intervention for trigonocephaly (typically during months 3-6 of life) produces superior cosmetic outcomes 6