NORMAL LABOUR Flashcards
How many stages of labour are there?
3
When does the first stage of labour begin?
Painful regular contractions (prior to this there will be painless irrugelar uterine tightenings)
Cervical dilatation of 4 cm or more and effacement
What is effacement, in the context of labour?
When the cervix has spread so far that it now becomes part of the uterine lining.
Other than regular contractions and cervical dilatation, what else might happen that may signal (but not define) the beginning of labour?
Show - passage of a mucoid plug from the cervix, often blood stained
Rupturing of membranes
When does the first stage of labour end and the second stage begin?
Full dilation - 10 cm
What is monitored in the first part of labour?
Uterine contractions
Dilation of cervix
Descent of presenting part
What is the normal rate of cervical dilatation in nulliparous women in the first part of labour?
0.5-1 cm/h
What is the normal rate of cervical dilatation in multiparous women in the first part of labour?
1-2 cm/h
What is the name of the chart used to document the observations made in labour? What is the purpose of this chart?
Partogram - used to highlight slow progress, particularly a delay in cervical dilatation or failure of the presenting part to descend.
What are the three factors (3 P’s) that determine the progress through labour?
Passages
Passenger
Power
What are the boundaries of the pelvic inlet?
Pubic crest
Iliopectineal line
Sacral promontory
The widest diameter of the pelvic inlet lies in which line?
Transverse
How wide is the widest diameter of the pelvic inlet?
13 cm
What are the boundaries of the pelvic outlet?
Lower border of the pubic symphysis
Ischial spines
Tip of the sacrum/coccyx
The widest diameter of the pelvic outlet lies in which line?
Anteroposterior
How wide is the widest diameter of the pelvic outlet?
11 cm
What are the muscles of the pelvic floor that the fetus must pass through?
Levator ani group:
Pubococcygeus
Iliococcygeus
Internal obturator
Piriformis
What part of the anatomy is responsible for the propulsive contractions that deliver the fetus?
The upper uterine segment
What are the 3 layers of the myometrial component of the uterus?
Thin outer longitudinal layer
Thin inner circular layer
Thick middle spiral layer
When do uterine contractions start in pregnancy?
Quite early on. There are painless irregular contractions that will start from as early as the second trimester.
What do we call the painless, irregular contractions that start early on in pregnancy?
Braxton-Hicks contractions
What is progressive retraction, in the context of labour?
This describes the ability of the uterine muscles to not only relax and contract but to become progressively smaller resulting in dilatation of the cervix and eventually effacement.
What about the contractions during labour do we monitor ?
Strength
Frequency
Duration
In the first part of labour what is the usual range of rate of contractions?
Starts at about 2/3 contractions every 10 minutes and progresses to about 4/5 over 10 minutes. Each one lasting 60s.
As well as the uterus, which other muscles does the mother recruit in order to help with delivery of the baby?
Diaphragm
Abdominal muscles
What bones make up the cranium of the fetus?
2 frontal bones
2 parietal bones
1 occipital bone
What is the name of the suture that sits in between the frontal bone and the parietal bone in the cranium of the fetus?
Coronal suture
What is the name of the suture that sits in between the parietal bone and the occipital bone?
Lambdoid suture
What is the first step in the delivery of the fetus?
Engagement of the head into the pelvic inlet
What direction should the fetus be for engagement of the head into the pelvic inlet?
Occipito transverse
After the fetus’ head has engaged with the pelvic inlet, what is the next step in the delivery of the fetus?
Flexion of the head to allow the fetus to end up so that the suboccipitobregmatic diameter (smallest diameter) is presenting.
Also internal rotation so baby ends up occipito anterior to allow head to line up with pelvic outlet.
Once the fetus has rotated to an occipito anterior position to allow the head to line up with the pelvic outlet, what is the next step in the delivery of the fetus?
The head is delivered. The occiput descends first and then the head is delivered by extension. Further extension delivers the face.
Delivery of the head also brings the shoulders through the pelvic inlet into the pelvic cavity.
Once the head is delivered, what is the next step in the delivery of the fetus?
Restitution or external rotation. The head and then the shoulders rotate to an occipito transverse position to allow the shoulders to the line up with the widest pelvic outlet diameter.
Once restitution has occurred, what is the next step in the delivery of the fetus?
Further contractions and gentle downward traction of the head allows the shoulders to come through the pelvic outlet.
Lateral flexion of the fetus delivers the anterior then posterior shoulder and the rest of the body follows.
Summarise the 6 steps of delivery of the fetus.
- Engagement of fetal head in pelvic inlet
- Flexion of fetal head
- Internal rotation to line up with pelvic outlet
- Extension to deliver head and face
- Restitution or external rotation
- Lateral flexion to deliver anterior shoulder and then the rest of the body.
When does the second stage of labour end and the third stage begin?
Birth of the baby
When does the third stage of labour and hence labour overall end?
With the delivery of the placenta and membranes
What should be done as part of the regular examination of the mother during the first part of labour?
- Obs (HR, RR, BP, temp)
- Urinalysis
- Analgesia requirements
- Abdominal palpation: fundal height, lie, presentation, engagement
- Contractions: strength, frequency, duration
- Vaginal examination: degree of cervical effacement, cervical dilatation, station of presenting part in relation to ischial spines, position of presenting part, presence of caput or moulding.
Once the membrane ruptures, what must you document about it?
Clear
Blood stained
Meconium
What are mothers encouraged to do in the first part of labour?
Mobilise
Are mothers allowed to eat during labour?
Yes, unless there is a chance that they will need to have general anaesthetic. Remember that there is delayed gastric emptying during labour.
What are the different categories of analgesia used in labour?
Oxygen/nitrous oxide
Opioids
Pudendal block
Perineal infiltration
Epidural anaesthesia
Spinal anaesthesia
When do we give oxygen/nitrous oxide to women in labour?
In the first part of labour, an inhalation of 50:50 mixture with onset of contractions. Works on less than 50% of women.
What is the opioid classically used as analgesia in labour? Include route and dose.
Pethidine IM 100-150 mg
Must give with an antiemetic such as cyclizine
How effective is pethidine in the control of pain during labour?
Works in less than 50% of women.
What are the side effects of pethidine?
Nausea and vomitting (must give with an antiemetic)
Respiratory depression of the neonate - can be easily reversed with naloxone IM
How is a pudendal block performed for the control of pain in labour?
Infiltration of right and left pudendal nerves (S2, S3 and S4) with 0.5% lidocaine.
When during labour is a pudendal block typically used?
Second stage of labour
How is perineal infiltration performed for the control of pain in labour?
Infiltration of perineum with 0.5% lidocaine at posterior fourchette
What is the indication for perineal infiltration as pain control during labour?
Perineal infiltration is only done as pain relief prior to an episiotomy. It will be used again in the third stage of labour for suturing of perineal lacerations.
How is an epidural performed for the control of pain in labour?
Injection of 0.25-0.5% bupivicaine via a catheter into epidural space
What spinal level is epidural performed at for the control of pain in labour?
L3-L4
At what stage in labour can an epidural be given?
First or second stage
or before a caesarian section
What are the side effects of an epidural when used in the control of pain in labour?
Transient hypotension
Risk of dural tap
Increased length of second stage because of reduced pelvic floor tone and loss of bearing down reflex
How is spinal anaesthesia performed for the control of pain in labour?
Injection of 0.5% bupivicaine into sub-arachnoid space
What are the indications for spinal anaesthesia for the control of pain in labour?
Any operative delivery
Manual removal of the placenta
How do we manage mothers in the third part of labour to decrease the risk of postpartum haemorrhage?
Use oxytocic drugs
Clamping and cutting of the cord
Controlled cord traction
What forms of oxytocin are used in the third part of labour?
Syntocinon - 5 units of oxytocin
Syntometrine - oxytocin with 0.5 mg of ergometrine
Both given IM
What is the method of controlled cord traction most commonly used to deliver the placenta?
Brandt-Andrews’ method - pushing down on the lower abdomen just above the pubic symphysis, whilst gently pulling on the cut cord. This is done to prevent uterine inversion.
What is a physiological 3rd stage of labour?
They do not receive any oxytocic drugs, the attendant waits for the umbilical cord to stop pulsating before cutting it and delivery of the placenta occurs passively.
Why would you decide to perform active management of the 3rd stage of labour rather than passive physiological 3rd stage?
Situations where there is an increased risk of PPH or parental choice.
What are the final checks that must be done at the end of the third stage of labour?
Vagina, labia and perineum are examined for lacerations
Uterine fundus is palpated to check that it is well contracted, approximately at the level of the umbilicus.
Estimated blood loss should be recorded.
What are the indications for inducing labour?
Severe pre-eclampsia Recurrent antepartum haemorrhage Pre-existing disease eg diabetes Prolonged pregnancy (more than 41 weeks) Intrauterine growth restriction of the fetus Rhesus disease Multiple pregnancy (37 weeks)
What are the three main methods of inducing labour?
1st line - topical prostaglandins
2nd line - Amniotomy
3rd line - Oxytocin
What prostaglandins are normally used in the induction of labour?
Local application of prostaglandin E2 given as a vaginal gel or tablet.
What is amniotomy and how is it performed?
Artificial rupture of the membranes induces labour by causing local release of endogenous prostaglandins. It is done using an amnihook.
By what route is oxytocin given to induce labour?
IV. It is often given after amniotomy. The dose must be carefully titrated according to the strength and frequency of the uterine contractions.
