Timings At how many weeks gestation can a woman go into what is
known as labour? 24 weeks + 42 weeks
Slide 3
Terms What is the lie? Describes the relationship of its long
axis to the long axis of the uterus. The commonest lie is
longitudinal What is the presentation? The presentation of the
fetus describes which part is adjacent to the pelvic inlet. What
are the 5 presentations? And which is the most common? Vertex most
common 96% Breech Shoulder Face Brow What is the pelvic inlet?
(think tunstall) The pelvic inlet is bounded posteriorly by the
sacrum; laterally by the ilio-pectinal line and anteriorly by the
superior pubic rami and the upper margin of the pubic symphysis.
Normally the pelvic inlet is 11cm Have a go at naming these
presentations and lies.
Slide 4
Stages of labour What are the three stages of labour? Creation
of birth canal: onset of labour until 10cm dilated Delivery of
foetus: from 10cm dilatation until the baby is delivered Delivery
of placenta and management of blood loss How do you define going
into labour? -Onset of uterine contractions and cervix effacement
and dilation. How are labour contractions different to Braxton
Hicks contractions? Labour contractions are: more intense, more
frequent and last longer than BH contractions which become
noticeable from 16 weeks.
Slide 5
Stage 1 The onset of labour is relatively sudden in the
frequency and force of contractions. Which 3 hormones are
implicated in this change?: Prostaglandins, relaxin & oxytocin.
What is cervix effacement? Thinning of the cervix. Until labour,
the cervix is about 4cm long, tightly closed & protected by a
mucous plug. What triggers the cervix to thin and soften (aka
ripening)? Prostaglandins inhibit collagen synthesis, stimulate
collagenase activity and increase in glycosaminoglycans (GAGs)
Consequently leads to a break down in collagen Influx of
inflammatory cells and increase in Nitric oxide
Slide 6
Stage 1 What is cervix dilatation? -With a thinner cervix, it
is able to dilate so that the babys head is in place What is meant
by the show? -The cervix mucous plug is released (can happen before
labour) -Normally pink in colour What is meant by waters have
broken? - The fetal membranes rupture releasing amniotic fluid.
What is meant by brachystasis? After each contraction, the uterine
smooth muscle fibres shorten and do not relax fully. This shortens
the uterus and pushes the baby down further.
Slide 7
Ferguson reflex Describe the Ferguson reflex(4 points) 1.Babys
head stretches cervix and feedbacks on pituitary 2.Pituitary
secretes oxytocin into blood and travels to uterine muscle
3.Oxytocin stimulates uterine contractions and pushes baby down,
stretching the cervix further 4.Cycle repeats over and over Where
is oxytocin synthesized? Produced by the hypothalamus and STORED
and secreted by the posterior pituitary gland.
Slide 8
Stage 2 This stage is relatively quick: 1-2+ hours. Internal
rotation to bring shoulders through pelvis. How is progress
measured? (hint - 1,-2,-3cm...) Descent of head is described
relative to ischial spines upon vaginal examination. The station is
recorded. (ischial spines are at station 0) The biggest risk here =
tearing of perineum What can be done to reduce this? Episiotomy.
Preferably medio lateral to protect anal sphincter
Slide 9
Stage 3 In this stage the placenta is separated from uterus by
powerful uterine contraction. Placenta + membranes are expelled.
This takes 10-30 mins What can help this along? Oxytocin drug Cord
traction (pull the cord whilst applying pressure) What is the
normal amount of blood loss during delivery? 500ml Use of oxytocic
reduces the risk of postpartum haemorrhage (>1000ml)** What is
involution? Process by which the uterus is transformed from
pregnant to non pregnant state. This is primarily due to oxytocin
often inject this in order to speed up the process.
Slide 10
What are the 3 Ps of labour? Power: frequency, amplitude and
duration Passage: bony pelvis and soft tissue Passenger: size, lie,
presentation and well being. What is the name of the graph used to
monitor progression of labour? Partogram
Slide 11
Question time! Kate is in labour What are the 3 stages of
labour? Willy is getting nervous and wants the foetus checked. What
is normal heart rate, variability, deacclerations and
accelerations? 100-160bpm Variability >5 Decelerations none
Accelerations - present Kate demands a spinal anaesthetic. What
layers does this go through? And in what space does the needle end
up? Skin, subcutaneous fat, supraspinous, interspinous, ligamentum
flavum, dura, arachnoid and into the subarachnoid space. What are
the role of prostaglandins in labour?
Slide 12
Question time! Kate is getting bossy and wants to know why she
is on so much pain. What is the pelvic pain line?