Transcript The Mechanism of Labour

Mechanism of labour
Descent
The fetus begins to
descend into the pelvis
due to the force of gravity
and downward pressure
of the contractions
Relation to practice
Primip-may occur before the
onset of labour
Multip-not until onset of
labour due to laxity of
uterine/abdo muscles
Educate re optimal fetal
positioning
Adequate abdominal palpation
Upright and mobile once in
Labour, continual support
Claire Allan
1
Mechanism of labour
Flexion
As the fetus descends the chin
touches the chest (arms begin
to cross) and the attitude of
flexion is adopted. This is
increased further when the
head meets the resistance of
the birth canal
Relation to practice
Upright position to assist with
gravity
When resting, adopt the left
lateral position (OFP)
Observation of the
contractions-are they regular,
do they appear to be
increasing in strength and
becoming expulsive?
Claire Allan
2
Mechanism of labour
Internal rotation
As the occiput reaches the
resistance of the pelvic floor, it
rotates forward 45 degrees.
The slope of the pelvic floor
aids this rotation forward and
allows the head to emerge in
the longest diameter of the
pelvis (anterposteior)
Relation to practice
Fully dilated, station of the head
Vertex may or may not be
visible
Upright position-kneeling,
squatting
May be spontaneously pushing
Would you encourage
mechanical pushing or allow
for natural descent?
Claire Allan
3
Mechanism of labour
Crowning
The head has crowned when it
escapes under the pubic arch
and no longer recedes
between contractions because
the widest transverse diameter
of the head is born
Extension
With slight extension the
bregma, forehead, face and chin
will pass over the perineum and
the head is born
Relation to practice
May be
spontaneously/mechanically
pushing or still breathing
through contractions, how
long can the second stage last?
Introverted in her behaviour
and may adopt alternative
Position, bending towards the
floor with knees apart
Claire Allan
4
Mechanism of labour
Restitution
When the head is born it will
turn to the left or the right,
righting itself with the
shoulders. The shoulders then
rotate (similar action to that of
the head) and lie in the
anteroposterior diameter of
the pelvis. Rotation follows
the same direction as restitution
Relation to practice
No need to do anything, allow
time for restitution (you may
see a small part of the anterior
shoulder). Wait for the next
contraction to deliver the
remainder of the body
(Dr’s are often too quick in
trying to deliver the body)
Claire Allan
5
Mechanism of labour
Lateral flexion
In most supine or semi
recumbent birthing positions
the anterior shoulder will be
born first (under the pubic
arch) and the posterior
shoulder will pass over the
perineum
Relation to practice
If the woman is on all fours or
leaning forward then the
posterior shoulder may be
born first due to gravity and
the effect of the birth canalthe curve of carus-this causes
the trunk of the baby to flex
sideways as it is born
Claire Allan
6