CEPHALIC PROMINENCE The most prominent part of the head palpable per abdomen Produced by flexion and extension of the head Vertex presentation (head well flexed) occiput is lower than sinciput (can be felt on the side opposite to the back)
When the presenting part is face or brow (extension of head) sinciput is lower than occiput (can be felt on the same side of the back) Cephalic prominence can be palpated by the second pelvic grip
When no cephalic prominence is felt, there is neither flexion nor extension and the attitude is one of deflexion . This is also called military position
Longitudinal lie commoner –fetus being an ovoid accommodates itself easily along the long axis of the uterine ovoid Cephalic presentation commoner -the head being heavier and more compact , due to gravitation, comes to occupy lower pole and bulkier breech adapts to the fundus of uterus ,which is roomier
MOULDING Cranial bones are connected by membrane and this allows considerable shifting or sliding of each bone to accommodate to the maternal pelvis. Frontal and occipital bone pass under parietal bone. Posterior parietal is subject to more pressure by the sacral promontory , it passes under anterior parietal.
MOULDING (conti…..)Thus there is compression of the presenting diameter with compensatory bulging of the diameter at right anglesEg: in occipitoanterior head is compressed in the presenting suboccipitobregmatic and elongated in the verticomental diameter .
Moulding is assessed on vaginal examination at two sites parietal-parietal parietal-occipital• disappears a few hrs after birth• Protective mechanism & prevents the fetal brain from compression as long as it is not excessive or not rapid
Clinical significance Some amount of moulding is beneficial and this is one of the factors which decide the success of a trial of labour Severe moulding can lead to intracranial haemorrhage The site of moulding gives information about the position of the head