RELATION BETWEEN FETUS & PELVIS

LIE PRESENTATION PRESENTING PARTS ATTITUDE DENOMINATOR POSITION CEPHALIC PROMINENCE

LIE The relationship b/w the long axis of fetal ovoid to the long axis of uterine ovoid LONGITUDINAL LIE TRANSVERSE LIE OBLIQUE LIE

PRESENTATION That part of the fetus that lies over the pelvic inlet & occupies the lower poles of the uterus 3 presentation CEPHALIC PODALIC/BREECH SHOULDER

PRESENTING PARTS The most dependant part of the fetus, which is felt first on vaginal examination In cephalic presentation depending upon degree of flexion, vertex brow face deflexed head

In breech presentation Flexed breech (fetal legs may be flexed) Extended breech (extended at knees) Footling breech (completely extended)

ATTITUDE The relation of fetal parts to each other Main attitudes FLEXION EXTENSION

TYPICAL FETAL ATTITUDE universal flexion with head flexed over chest, arms & legs flexed in front of the body and back curved forward

Anteroposterior diameters of the fetal skull AP diameter Attitude Presenting part Suboccipitobregmatic 9.4 cm Complete flexion Vertex occipitoanterior Suboccipitofrontal 10.5 cm Incomplete flexion Vertex occipitoposterior Occipitofrontal 11 cm Deflexion Verticomental 13.5 cm Extension Brow Submentobregmatic 9.4 cm Complete extension face

DENOMINATOR An arbitrarily chosen point on the presenting part of the fetus which is used to describe the position.

Presentations of the fetus Attitude Denominator Cephalic vertex occipitoanterior Flexion Occiput vertex occipitoposterior Deflexion occiput brow Extension face Complete extension Chin or mentum Podalic or breech sacrum shoulder acromion

Frequency of lie and presenting part Presentation and presenting part Longitudinal 99.5% Vertex 96% Transverse or oblique 0.5% Face 0.5% Brow 0.5% Breech 3% Shoulder 0.5%

POSITION The relationship of the denominator to the four quardrants of the maternal pelvis.

In vertex presentation Left occipitoanterior(common) Left occipitotransverse Left occipitoposterior Right occipitoanterior Right occipitotransverse Right occipitoposterior

Occipitoanterior

Left occipitoposterior

LeftOccipitoanterior

LeftOccipitotransverse

Occipitoposterior

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 angles Eg: 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

GRADING Grade 1 / +moulding :obliteration of suture line Grade 2 / ++moulding : reducible overlap Grade 3 /+++moulding:irreducible overlap (pathological)

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

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