and Paula Briggs2
(1)
Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia
(2)
Sexual and Reproductive Health, Southport and Ormskirk Hospital, Southport, UK
Breech, Transverse & Unstable Lie, Brow, Face & Compound Presentation
Definition
Any presentation that is not a longitudinal lie with a vertex presentation is said to be a malpresentation.
A Breech presentation is when the baby’s feet or buttocks are presenting in the pelvis.
A transverse/oblique lie is when the head is not in the pelvis and the fetus is in a horizontal position.
An unstable lie is when the presenting part changes position.
A brow presentation is when the head is deflexed and instead of the vertex, the brow presents.
A compound presentation is when there is a head or a breech plus a limb presenting.
Incidence
Although one in five fetuses are a breech presentation at 28–32 weeks, by term most turn to a cephalic presentation, with only one in 25 persisting a breech presentation. Transverse and unstable lie are uncommon. Brow and compound presentations are only diagnosed in labour, and are vey uncommon.
Aetilogy and Pathogenesis
Most babies are in a cephalic presentation as the natural shape of the foetus matches the shape of the uterine cavity (Fig. 23.1). Any factor that changes this “best-fit” relationship can predispose to malpresentation.
Fig. 23.1
The shape of the foetus matching the shape of the uterus
To analyse possible causes one can use the “Passengers/passages/powers” framework.
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