Lecture 8.1: Parturition Flashcards
What is Labour?
A series of continuous, progressive contractions of the uterus that help the cervix dilate and efface that results in expulsion of products of conception after 24 weeks
When in the pregnancy is it classed as Spontaneous Abortion?
Before 24 weeks
When in the pregnancy is the baby classed as Pre-Term?
Before 37 weeks
When in the pregnancy is the baby classed as Term?
37-42 weeks
When in the pregnancy is the baby classed as Post-Term?
After 42 weeks
How many Stages of Labour are there?
3
What happens in Stage 1 of Labour?
- Interval between the onset of labour and full cervical
dilation - Creation of the birth canal
What are the 2 Phases of Stage 1 of Labour?
- Latent phase: onset of labour with slow cervical
dilation to ~4 cm and variable duration - Active phase: faster rate of cervical change, 1-1.2 cm
/hour, regular uterine contractions
What happens in Stage 2 of Labour?
Delivery of the foetus
What happens in Stage 3 of Labour?
Delivery of the placenta and membranes
Three Ps of Labour
- Powers
- Passenger
- Passage
When is the Dating Scan done? What does it show?
- Approx. 12 weeks
- Confirms dates and identifies singleton or multiple
pregnancy
By what week is the Uterus palpable?
12 weeks
By what week does the Uterus reach the umbilicus?
20 weeks
By what week does the Uterus reach the Xiphisternum?
36 weeks
How to describe baby’s position in uterus towards the end of the pregnancy
- Lie: Longitudinal/Oblique/Transverse
- Presentation: Cephalic/Breech
- Anterior/Posterior
- Occipital/Sacral
How much does cervix dilate in labour?
Up to 10cm
Maximum size of birth canal determined by pelvis, how large is the Pelvic Inlet typically?
- 13.5cm X 11 cm
- Softening of ligaments may increase it
After 36 weeks, the presenting part of the baby..?
“Sinks” into pelvis, known as the “lightening”
Does “lightening” occur in multi-parous women?
- Happens less in multi-parous women
- Multi-parous women often have some painful powerful
contractions a few days before - But not regular and not effective in dilating the cervix
Creation of the Birth Canal
- Expansion of soft tissues
- Lower uterine segment
- Cervix
- Vagina
- Perineum
- Some relaxing of ligaments to increase pelvic inlet,
cavity and outlet
What is ‘cervical ripening’?
The normal process of softening and opening the cervix before labor starts
What processes occur during ‘cervical ripening’?
- Reduction in collagen
- Increase in glycosaminoglycans
- Reduced aggregation of collagen fibres
What triggers ‘cervical ripening’?
- Triggered by prostaglandins
- PGE2 and F2-alpha
What is the structure of the cervix throughout most of the pregnancy?
- Cervix retains foetus for most of pregnancy
- Tough, thick walled 3 cm canal
- Collagen
- Cervical incompetence
What is Cervical Effacement?
Effacement means that the cervix stretches and gets thinner
‘Braxton-Hicks’ Contractions
Also known as prodromal or false labor pains, are contractions of the uterus that typically are not felt until the second or third trimester of the pregnancy, they are the body’s way of preparing for true labor
Uterine contractions have two major goals, what are they?
- To dilate cervix
- To push the foetus through the birth canal
Contractions made more forceful and frequent by…?
- Prostaglandins (more Ca2+ per action potential)
- Oxytocin (more action potentials, lower threshold)
What are Prostaglandins? Where are they mainly produced?
- Biologically active lipids
- Local hormones
- Produced mainly in endometrium
What is production of Prostaglandins controlled by?
Production controlled by oestrogen progesterone ratio
What effect do Prostaglandins have?
- Powerful contractors of smooth muscle
- Involved in cervical softening
What is a Low Oestrogen-Progesterone Ratio? What effect does this have on Prostaglandins?
- Progesterone>Oestrogen
- Low Prostaglandins
What is a High Oestrogen-Progesterone Ratio? What effect does this have on Prostaglandins?
- Oestrogen>Progesterone
- Increased Prostaglandins
What is Oxytocin?
Oxytocin is a peptide hormone, as an important role in many human behaviours including sexual arousal, recognition, trust, romantic attachment and mother–infant bonding
Where is Oxytocin secreted from?
- Secreted by posterior pituitary
- Controlled by hypothalamus
What is the Ferguson Reflex?
A neuroendocrine reflex in which the foetal distension of the cervix stimulates a series of neuroendocrine responses, leading to oxytocin production
What hormone induces oxytocin receptors on uterus?
Oestrogen from ovaries
What is Induced Labour?
Artificially stimulated labour
What is the Bishop Score?
- A calculation used to predict how close you are to
labor - A Bishop score of 8 or greater is considered to be
favorable for induction
What conditions may indicate induction of labour? (3)
- Severe preeclampsia
- Recurrent antepartum haemorrhage
- Pre-existing disease (diabetes)
What are the 3 Induction Methods?
- Prostaglandin
- Oxytocin
- Amniotomy
Induction Method: Prostaglandin
- Locally applied PE2 as vaginal gel, tablet or pessary
- Ripens cervix and reduces incidence of operative
delivery when compared to use of oxytocin alone - NICE guidance reg. dose to reduce risk of
hyperstimulation of uterus
Induction Method: Oxytocin
- IV infusion of synthetic oxytocin
- Post amniotomy or SROM
- Requires careful dose titration in accordance with
frequency and strength of contractions - Requires constant foetal monitoring
Induction Method: Amniotomy
- Thought to cause local release of endogenous PG
- Done using amnihook
Complications of an Amniotomy? (6)
- Cord prolapse
- Infection
- Bleeding from vasa praevia
- Placental separation
- Failure to induce efficient contractions
- Amniotic fluid embolism
What is a Cardiotocography?
A continuous recording of the foetal heart rate obtained via an ultrasound transducer placed on the mother’s abdomen
What can happen to the foetal heart rate during contractions?
- It can slow down but should return to normal post-
contraction - If bradycardia persists, it is a sign of foetal distress
With each contraction the baby descends, how can this descent be measures?
- This can be assessed per vagina
- Position relative to ischial spines
During the 2nd Stage of Labour, the baby’s head rotates internally and meets resistance of the …… ……. , the …… is “leading” and meets the sloping “gutter” of the ……. ……
- Pelvic Floor
- Occiput
- Levator ani
Head extends when the occiput “escapes” from under the …… ……
Symphysis Pubis
What is an Episiotomy?
A surgical cut made at the opening of the vagina during childbirth, to aid a difficult delivery and prevent rupture of tissues
What is Restitution?
When the head is delivered it rotates back to the neutral position with the occiput facing the thigh
How many degrees of Tears are there?
4
What happens in a 1st Degree Tear?
Small tear in skin and vaginal epithelium
What happens in a 2nd Degree Tear?
Tears are deeper and affect the muscle of your perineum
What happens in a 3rd Degree Tear?
Tears also involve the anal sphincter
What happens in a 4th Degree Tear?
Tears goes further into the lining of your anus or bowel
What positions can help make labour easier? (6)
- Walking and Standing
- Kneeling
- Sitting
- Use a birthing ball
- Supported standing or squatting
- Rock on all fours or rock your pelvis in whatever
position you find comfortable - Water Birth
What Analgesia can be given during Labour? (6)
- Oxygen/nitrous oxide (Entonox)
- Paracetamol
- Pethidine
- Pudendal block
- Epidural
- Spinal anaesthesia
Why may a Failure to Progress in Labour occur: Passage Issues (5)
- Abnormal Shaped Pelvis
- Cephalopelvic Disproportions
- Uterine/Cervical Fibroids
- Cervical Stenosis
- FGM
Why may a Failure to Progress in Labour occur: Passaenger Issues (4)
- Foetal Size
- Foetal Abnormality
- Foetal Malpresentaion
- Foetal Malpostion
Why may a Failure to Progress in Labour occur: Power Issues
Lack of co-ordinated regular strong uterine contraction
What is an Assisted Birth/Operative Vaginal Delivery?
Operative vaginal delivery is a vaginal delivery that is assisted by the use of forceps or a vacuum extractor
What is a Cesarean Section?
An operation to deliver your baby through a cut made in your tummy and womb
When does 3rd Stage of Labour commence and end?
- Commences with the completed birth of the baby
- Ends with the complete expulsion of the placenta and
membranes
How long does 1st Stage of Labour last?
- 12 to 19 hours
- It may be shorter for moms who’ve already had
children
How long does 2nd Stage of Labour last?
- Within 3 hours of the start of active pushing in most
women having their first baby - Within 2 hours for most women who have had a baby
before
How long does 3rd Stage of Labour last?
Usually lasts between 5 and 15 minutes but any period up to 1 hour may be considered within normal limits
Immediately after delivery of baby, the uterus becomes
quiescent for a few minutes, what does this mean?
It is a period of active relaxation of the myometrial smooth muscle cells
How does Placenta expulsion occur?
- Uterus contracts down hard (A)
- Shears off placenta (B)
- And expels it
Uterine Retraction and Placental Separation
- Blood in intervillous space forced back into veins of
spongy layer of decidua basalis - Veins become tense and congested and kept under
pressure by underlying muscle layer of uterus - Blood can’t drain back into maternal bloodstream
because uterus has retracted and doesn’t allow it
What is the importance of uterine contraction in the 3rd Stage of Labour?
- Compresses blood vessels
- Reduce haemorrhage
What is Postpartum Haemorrhage?
Bleeding form the genital tract of more than 500ml after delivery of the infant
What are the 2 Types of Postpartum Haemorrhage?
- Primary: Within 24hrs
- Secondary: Between 24hrs and 6 weeks
How often does Postpartum Haemorrhage occur?
Incidence in 5% of deliveries
When does Postpartum Haemorrhage become clinically significant?
- Clinically loss of >1000ml more clinically significant
- > 1500ml major obstetric haemorrhage
What is Antepartum Haemorrhage?
Bleeding from or in to the genital tract, occurring from 24+0 weeks of pregnancy and prior to the birth of the baby
Why may Antepartum Haemorrhage occur? (3)
- Normally sited placenta: Abruptio placentae
- Low lying placenta: Placenta praevia/Vasa praevia
- Another cause such as cervical cancer/cervical erosion
What is Abruptio placentae?
Occurs when the placenta partly or completely separates from the inner wall of the uterus before delivery
What is Placenta praevia?
- Low lying placenta attached to the lower uterine
segment - Partly attached to the lower segment to covering the
whole of the internal cervical os
What is Vasa praevia?
A very rare condition where blood vessels travelling from your baby to your placenta, unprotected by placental tissue or the umbilical cord, pass near to the cervix
Symptoms of Antepartum Haemorrhage (4)
- Vaginal Bleeding
- Abdominal Pain
- Uterine Contractions
- Uterine Tenderness
What System is used for Assessment of the Newborn?
Apgar Scoring System
What does APGAR stand for?
Activity (muscle tone)
Pulse
Grimace (reflex irritability)
Appearance (skin colour)
Respiration
How is APGAR Scored?
- Each section scored 0-2
- Total score of 1 to 10
- A score of 7, 8, or 9 is normal and is a sign that the
newborn is in good health.
What happens when the neonate takes its first breath?
- Reduces pulmonary vascular resistance
- Increases arterial PO2
- Left arterial pressure exceeds right
- Foramen ovale closes
- Ductus arteriosus contracts in response to raised pO2
- Foetal converts to adult circulation
What is Shoulder Dystocia?
When the baby’s head has been born but one of the shoulders becomes stuck behind the mother’s pubic bone, delaying the birth of the baby’s body
What 2 Manoeuvres are performed to help in the case of Shoulder Dystocia?
- Woods Corkscrew Manoeuvre
- McRoberts Manoeuvre
Woods Corkscrew Manoeuvre
The obstetrician places a hand on the anterior aspect of the posterior foetal shoulder and rotates the shoulder toward the foetal back
McRoberts Manoeuvre
- Hyperflex maternal hips (knees to chest position) and
tell the patient to stop pushing - This widens the pelvic outlet by flattening the sacral
promontory and increasing the lumbosacral angle - This single manoeuvre has a success rate of about
90% and is even higher when combined with
‘suprapubic pressure’
What is Erb’s palsy?
The infant’s arm hangs limply from the shoulder with flexion of the wrist and fingers due to weakness of muscles innervated by cervical roots C5 and C6
What is Klumpke’s palsy?
- A form of brachial plexus palsy
- Paralysis of the arm
