Stages of labour Karina Bennett & Melissa Brittle

Timings At how many weeks gestation can a woman go into what is known as “labour”? – 24 weeks + – <24 weeks = spontaneous abortion / miscarriage At how many weeks gestation is it considered preterm? – <37 weeks – Term = weeks – Post-term = >42 weeks

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….

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.

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 (GAG’s) – Consequently leads to a break down in collagen – Influx of inflammatory cells and increase in Nitric oxide

Stage 1 What is cervix dilatation? -With a thinner cervix, it is able to dilate so that the baby’s 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.

Ferguson reflex Describe the Ferguson reflex…(4 points) 1.Baby’s 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.

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

Stage 3 In this stage the placenta is separated from uterus by powerful uterine contraction. Placenta + membranes are expelled. This takes 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.

What are the 3 P’s 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

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? – bpm – 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?

Question time! Kate is getting bossy and wants to know why she is on so much pain. What is the pelvic pain line?