Etiology of Breech Presentation
Breech presentation results from multiple maternal, fetal, and placental factors that prevent the fetus from assuming the normal cephalic position, with the most significant etiologies being prematurity, congenital anomalies, uterine abnormalities, and conditions affecting fetal mobility.
Primary Etiologic Categories
Fetal Factors
Congenital anomalies are strongly associated with breech presentation. Fetuses in breech have a 6.5% risk of congenital anomalies compared to 3.6% in cephalic presentation 1. The strongest associations include:
- Central nervous system malformations - impaired fetal movement and tone
- Musculoskeletal abnormalities - particularly hip dysplasia and deformities
- Respiratory system anomalies
- Female sex (consistently associated across studies) 2, 3, 4
The theory here is that breech presentation often represents a symptom of fundamental problems in fetal morphogenesis or neuromuscular function rather than simply a positional variant 1.
Gestational Age and Prematurity
The incidence of breech decreases dramatically with advancing gestational age, from 23.5% at 24-27 weeks to only 2.5% at term 2. This reflects the natural tendency for spontaneous version as pregnancy progresses and the fetus has adequate space and neuromuscular development to assume cephalic position.
Maternal Factors
- Advanced maternal age - consistently associated with increased breech risk 2, 3, 4, 5
- Nulliparity - higher rates in first pregnancies 2, 4, 5
- Previous cesarean section - doubles the odds (OR 2.13) 3
- Multiparity is protective - breech frequency decreases with increasing parity 4
- Ethnicity - Sub-Saharan African women have lower breech rates (2.62% vs 4.51%) 5
Uterine and Placental Factors
- Oligohydramnios (OR 1.42) - restricts fetal movement 3
- Placenta previa - mechanical obstruction 3
- Uterine anomalies (congenital or acquired)
- Previous uterine surgery or trauma
Pregnancy Complications
- Fetal growth restriction (OR 1.19) - smaller fetuses have altered mobility 3
- Preterm premature rupture of membranes - particularly significant in early preterm deliveries 2
- Gestational diabetes (OR 1.06) 3
- Pre-eclampsia/hypertension - especially in earlier gestational ages 2
Clinical Implications
The 2.4% term breech rate carries a significantly higher stillbirth rate (0.2% vs 0.1% in cephalic) 3, emphasizing that breech presentation itself represents a high-risk state beyond just delivery mechanics.
Common pitfall: Assuming breech is simply a random positional variant. The evidence clearly shows breech presentation clusters with multiple obstetric risk factors and should trigger comprehensive fetal evaluation, particularly for congenital anomalies 1.
Regarding "After-Coming Head" Delivery
The question mentions "delivery of after-coming head," which refers to the specific technique used during vaginal breech delivery or reverse breech extraction at cesarean. When an impacted fetal head occurs during cesarean delivery, reverse breech extraction is one management option where the baby's feet are grasped and delivered feet-first, with the head lifted out of the pelvis once shoulders are delivered 6. This technique carries risks of skull fractures, brain hemorrhage, and hypoxic brain injury 6.
For vaginal breech delivery, forceps can be used for the after-coming head 7, with various techniques including the Mauriceau-Levret-Veit-Smellie (MLVS) maneuver being commonly employed 8.