Second Stage Of Labour Flashcards
What does attitude mean?
Relationship between the fetal head and the limbs and trunk
What is meant by the lie?
Relationship of fetus to long axis of the uterus
What is meant by presentation?
Part of the fetus presenting in the lower aspect of the uterus
What is meant by position?
Relationship of presenting part to the maternal pelvis
What is the denominator?
Part of presenting part marking position (eg occiput)
What is the second stage of labour?
From full dilatation of the cervix to the birth of the baby.
Outline the characteristics of the transitional phase
Restlessness Desire for pain relief Stronger contractions but less frequent Rupture of membranes Expulsive contractions start
Outline characteristics in the woman in the second stage of labour
Vocal changes Eyes closing in concentration Breathing changes Increased vocalisation Involuntary bearing down
What are the outward signs of transition?
Natal line (purple line) Rhombus of michaelis Anal dilatation Vulval gaping SROM Mucous show
What is the rhombus of michaelis?
Kite shaped area of bone moves backwards during the second stage of labour as it pushes the wings of the ilea out increasing diameters in the pelvis
What is the Ferguson reflex?
Contractions become expulsive
Fetus descends further into vagina
Stimulation of nerve receptors in pelvic floor (positive feedback)
Woman wants to push.. Becomes compulsive
Secondary powers of expulsion abdominal muscles and diaphragm used
Outline the physical changes as the head descends
Soft tissue becomes displaced
Bladder pulled up anteriorly
Urethra becomes elongated and stretched and narrowed
Posterior lay rectum becomes flattened into the sacral curve
Pressure of advancing presenting part expels any fecal matter
Perineal muscles (Levator ani) dilate and thin
Perineal body flattens stretched and thins
Fetal presenting part visible at vagina
Advances with each contraction
Crowns, head born, shoulders follow
What position does the fetal head usually engage?
Occipito transverse as this is the widest diameter at the pelvic inlet
Descent then occurs
Outline flexion as a mechanism of labour
Due to pressure from contractions along the long axis of the fetal pole flexion of the fetal head is encouraged.
This is physiologically beneficial as it encourages the smallest diameter of the fetal head to pass through the pelvis
What is internal rotation?
The presenting part often the occiput hits the pelvic floor and will rotate forwards to lie underneath the symphysis pubis
It may now have adopted OA or OP position ideally OA
Outline extension as a mechanism of labour
Once crowning has occurred the head can extend by pivoting around the pubic bone releasing the sinciput, face and chin.
These are born by the movement of extension
Outline restitution as a mechanism of labour
The twist on the necks from the internal rotation is now corrected.
The occiput moves 1/8 of a circle towards the side at which it started
Outline external rotation as a mechanism of labour
The shoulders rotate into the AP diameter which is the weirdest pelvic output
Outline lateral flexion as a mechanism of labour
When mother is sitting the anterior shoulder is usually born first.
The anterior shoulder slips beneath the sub public arch and the posterior shoulder passes over the perineum
The remainder of the body is born by lateral flexion as the spine bends sideways through the curved birth canal
What physiological changes occur in the second stage?
Increased heat generated by muscle activity
Rise in maternal pulse
Pressure on sacral plexus and obturator nerve
How long does the seconds stage last?
NICE- birth would be expected to take place within 3 hours of the start of the active second stage in most nulliparous women and 2 hours in multiparous women
Time limits become prescriptive
There are no grounds for intervention if maternal and fetal condition is satisfactory
Steady progress is occurring evidenced by descent of presenting part
Outline the physiology of the second stage
Cervix becomes fully dilated and has incorporated into the lower segment of the uterus
Size of uterine cavity and therefore placental site is reduced
Shortened upper segment acts as a piston with each uterine contraction that pushes the fetus lower into the pelvic cavity
Pattern of strong repeated regular contractions
Mother compelled to bear down and push
Mother inspires before pushing
Diaphragm lowered
Abdominal muscles contract
Bearing down helps overcome resistance of the soft tissues of the vagina and pelvic floor
Fetal attitude extends and is directed through the birth canal
Outline the latent phases of the second stage
Full dilatation of cervix but presenting part not in pelvic outlet
No urge to bear down
Contractions may subside 10-12 mins
“Rest and be thankful”
Muscle fibres of uterine wall need to shorten and thicken further only when slack has been taken up can progress be made to expulsive contractions and descent
Stretch receptors in vagina, recumbent and perineum communicate change in volume,tension and tone
Passive cent should be allowed until presenting part visible
Outline the signs that birth is imminent
Congestion of vulva, dilatation, gaping of anus
Pass of faeces
Involuntary suing
Forewaters rupture
Maternal behaviour - vomiting, panic, anxiety, overwhelmed
Bright red vaginal loss
Woman more vocal, low grunting noises
Restless, strong desire to change position
Need to grasp
Outline the active phase of the second stage
Urge to push allows the presenting part to descend to compress the tissues of the pelvic floor
1cm above ischial spines nerve receptors are stimulated in pelvic floor (ferguson reflex) uncontrollable urge to push
Expulsive contractions
What is the fetal ejection reflex?
Steep rise in catecholamines during last minutes before birth leads to woman being very alert
Fetus releases them too wide eyed at mother
How is the fetal ejection reflex shown?
Sudden fear expressed in irrational way due to surge in hormones such as adrenaline
Immediately followed by irresistible contractions
What is the valsalva manoeuvre?
Forceful attempted exhalation against closed airways, closed glottis
What happens to the body in the valsalva manoeuvre?
Closed pressure system in the chest
Reduction in venous return
Reduction in cardiac output
Reduced BP
Reduced blood flow to placenta
Peripheral stasis in head and face (redness)
Maternal O2 levels reduced CO2 levels increased
Gasping for air causes sudden increase in BP, potential rupture of capillaries in face and neck
O2 to fetus reduced
What hormonal influences occur in labour?
Oxytocin
Accumulation in pregnancy causes memory loss, nesting behaviour, relaxed
Highly sensitive to stress and anxiety
Placental growth hormone levels decline in early labour
Sharp fall in prolactin levels 2 hours before birth
High circulating levels of oestrogen, progesterone and cortisol inhibit insulin secretion
Changes reduce maternal appetite, enhance maternal glucose tolerance and reduce insulin secretion
