Fetal Lie, Presentation, Attitude and Position
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Direct answer
Fetal lie, presentation, attitude and position describe how the fetus sits in the uterus. Lie is the fetal long axis relative to the uterus, presentation is the part lying over the pelvic inlet, attitude is the degree of head flexion, and position is the denominator relative to the maternal pelvis. The most common arrangement at term is a vertex presentation in the left occipito-anterior position.
What you must remember
- Lie: the relation of the fetal long axis to the uterine long axis, which is longitudinal in most term pregnancies, with transverse and oblique lies being uncommon.
- Presentation: the part of the fetus over the pelvic inlet, classified as cephalic (vertex, brow or face), breech or shoulder.
- Attitude: the degree of flexion of the fetal head, where flexion brings the suboccipitobregmatic diameter of about 9.5 cm into the pelvis.
- Denominator: the fixed landmark of the presenting part, such as the occiput, mentum, sacrum or scapula.
- Position: the relation of the denominator to the maternal pelvis, described as left or right and as anterior, posterior or transverse.
- Occipitofrontal diameter: about 11.5 cm, the wider diameter that presents when the head is extended rather than flexed.
- Abdominal diagnosis: a hard, round, ballotable head at the fundus means breech, whereas a soft, irregular breech at the fundus means vertex.
Presentations, denominators and palpation
Every presentation carries a denominator, and the position is named from it, so the pairs must be memorised together. Each row also gives the attitude and the abdominal feel, because examiners often describe the palpation findings and ask for the presentation.
| Presentation | Denominator | Typical attitude | Abdominal feel |
|---|---|---|---|
| Vertex | Occiput | Flexed, with the suboccipitobregmatic diameter engaging | Soft, irregular breech at the fundus |
| Face | Mentum | Fully extended, with the submentobregmatic diameter presenting | Breech at the fundus, with the head low in the pelvis |
| Breech | Sacrum | Hips flexed or extended, with the legs variable | Hard, round, ballotable head at the fundus |
| Shoulder | Scapula | Transverse lie, usually incompatible with vaginal birth | Fundus empty, with the head and breech felt at the flanks |
Breech is the commonest malpresentation at term, while shoulder presentation is rare but needs early planning. Abdominal palpation usually identifies the presentation before any internal examination, and ultrasound confirms it when the findings are unclear.
Where the exam tries to catch you
Most questions turn on mixing up the four terms, or on the side from which the position is named.
- Trap: confusing lie with presentation Correct: lie describes the fetal axis against the uterus, while presentation names the part lying over the pelvic inlet.
- Trap: naming the side from the examiner's viewpoint Correct: left and right refer to the mother's own left and right, whatever the examiner's position.
- Trap: treating a shoulder presentation as suitable for vaginal birth Correct: shoulder presentation usually requires caesarean section at term, unless the fetus is dead or very preterm.
- Trap: feeling a hard round head at the fundus and calling it a vertex Correct: a hard, round, ballotable head at the fundus means breech presentation.
Frequently asked questions
What is the difference between lie and presentation of the fetus?
Lie is the relationship between the long axis of the fetus and the long axis of the uterus, and it can be longitudinal, transverse or oblique. Presentation is the part of the fetus that lies over the pelvic inlet, such as the vertex, breech or shoulder.
What is the denominator in fetal presentation?
The denominator is the fixed landmark on the presenting part, used to name the fetal position relative to the maternal pelvis. It is the occiput for vertex, the mentum for face, the sacrum for breech and the scapula for shoulder presentation.
What is the normal attitude of the fetal head in labour?
The normal attitude of the fetal head in labour is flexion, with the chin on the chest. Flexion brings the smaller suboccipitobregmatic diameter of about 9.5 cm into the pelvis, rather than the occipitofrontal diameter of about 11.5 cm.
How does Leopold's manoeuvre identify breech presentation?
Leopold's manoeuvres identify breech presentation by feeling the fundus, where a hard, round, ballotable head is palpated instead of the soft, irregular breech of a vertex presentation. The lateral palpation and the fourth manoeuvre then help confirm the lie and the degree of engagement.
What is the most common fetal position at term?
The most common fetal position at term is left occipito-anterior, in which the occiput lies towards the mother's left side and the front of the pelvis. Most fetuses at term present by the vertex, and this position is the one examiners expect candidates to name first.