In a 29‑week pregnant patient with breech presentation, what is the likelihood of spontaneous conversion to cephalic before term and when should external cephalic version be considered?

Breech Presentation at 29 Weeks: Likelihood of Spontaneous Conversion

Most breech presentations at 29 weeks will spontaneously convert to cephalic by term, with approximately 50% of breech fetuses at 34 weeks turning spontaneously by 38 weeks, meaning the conversion rate from 29 weeks is even higher. 1

Natural History of Breech Presentation

• At 29 weeks, the majority of breech presentations will spontaneously rotate to cephalic before term, as 50% of breech fetuses still present at 34 weeks will turn by themselves to head down by 38 weeks 1
• The earlier the gestational age at which breech is identified, the higher the likelihood of spontaneous conversion to cephalic presentation 2
• By 35-36 weeks gestation, approximately 5% of singleton pregnancies remain in non-cephalic presentation, indicating that most earlier breech presentations have already converted 2

Timing for Intervention Consideration

• External cephalic version (ECV) should be considered at 37 weeks gestation, not at 29 weeks, as attempting version earlier risks the fetus returning to breech position 1
• ECV performed by an experienced practitioner at 37 weeks has a greater than 50% success rate, and in 95% of successful cases the head stays down until delivery 1
• Routine ultrasound examination at 35-36 weeks gestation is recommended to identify persistent non-cephalic presentations that may benefit from ECV 2

Management Algorithm for 29-Week Breech

• At 29 weeks, the appropriate management is expectant observation with reassessment at 35-36 weeks, as intervention at this early gestational age is not indicated 2, 1
• If breech presentation persists at 35-36 weeks, reassess after 1-2 weeks to allow for spontaneous rotation 2
• If non-cephalic presentation persists at 37 weeks, offer ECV with tocolysis to optimize success rates 3

Factors Affecting Spontaneous Conversion

• Spontaneous rotation from breech to cephalic is more likely with increasing interval between detection and delivery, meaning earlier detection (like at 29 weeks) allows more time for natural conversion 2
• Parous women have higher rates of spontaneous rotation compared to nulliparous women 2
• Transverse or oblique presentations are more likely to convert spontaneously than frank breech presentations 2
• The presence of polyhydramnios increases the likelihood of spontaneous rotation, while placenta previa decreases it 2

When to Consider ECV

• ECV should only be offered at 37-38 weeks for persistent breech presentation, not earlier, to avoid the fetus returning to breech position 1
• Parenteral beta stimulants (tocolytics) are effective in facilitating successful ECV, increasing the rate of cephalic presentation in labor (RR 1.68,95% CI 1.14 to 2.48) and reducing caesarean section rates (RR 0.77,95% CI 0.67 to 0.88) 3
• Regional analgesia combined with tocolysis is more effective than tocolysis alone for successful version (RR 0.61,95% CI 0.43 to 0.86) 3

Critical Pitfalls to Avoid

• Do not attempt ECV before 37 weeks, as the fetus may return to breech position and the natural rate of spontaneous conversion is high 1
• Do not diagnose "unstable lie" as an indication for labor induction after successful version from breech to cephalic, as this is not evidence-based 1
• Oligohydramnios is the only contraindication to ECV consistently mentioned across all guidelines, though evidence for most contraindications is limited 4