Fetal Presentation and Malpresentation
Definition
Fetal presentation:
- Refers to the part of the fetus that occupies the lower uterine segment and overlies the pelvic inlet
- In other words, the part that will enter the maternal pelvis first during labour
Fetal presentation is partly determined by the fetal lie:
- Fetal lie: the relationship between the long axis of the fetus (spine) and the long axis of the uterus (mother’s spine)
- Possible fetal lies: longitudinal, transverse or oblique
Normal Fetal Presentation
Normal fetal presentation (in ~96% of term pregnancies): cephalic presentation (fetal head is the presenting part)
However, there are several subtypes of cephalic presentation depending on the degree of head flexion:
- Vertex (the true normal presentation): head is fully flexed (→ occiput presents)
- Brow: head is partially extended (→ frotnum presents)
- Face: head is fully extended (→ mentum presents)
Malpresentation ≠ non-cephalic. As brow/face presentations sit within cephalic but are still abnormal.
Malpresentation covers:
- Non-cephalic presentations (e.g. breech, shoulder), AND
- Cephalic but non-vertex presentations (e.g. face, brow)
Normal covers only cephalic, vertex presentation.
Types of Fetal Malpresentation
Malpresentation: anything else apart from cephalic vertex presentation
| Malpresentation type | Prevalence | Definition (presenting part) | Main implications / complications | Management approach |
|---|---|---|---|---|
| Breech | 3-5% | Buttocks / feet
See the full Breech Presentation management. |
High Caesarean delivery rate
Vaginal delivery risks include:
|
3 options:
See the full Breech Presentation management. |
| Shoulder (transverse lie) | <0.5% | Shoulder | Spontaneous vaginal delivery is impossible
Complications:
|
Offer ECV at 36-37 weeks if diagnosed before labour
If ECV unsuccessful or labour has started → Caesarean delivery (often requiring classical vertical uterine incision) |
| Brow (subtype of cephalic) | 0.12-0.2% | Frontum (partially extended head) | Can result in arrested labour
<1/3 can result in vaginal delivery without converting |
Expectant management, as it often rotates to a deliverable position
If face presentation remains → Caesarean delivery ECV or instrumental manipulation are NOT recommended |
| Face (subtype of cephalic) | 0.1-0.12% | Mentum (fully extended head) | Spontaneous vaginal delivery is impossible
High perinatal mortality is associated with attempting vaginal manipulation |