Labour, Delivery and Analgesia Flashcards
When does normal delivery occur?
Between 39-41 weeks since date of last menstrual period
Within 24 hours of onset of regular contractions
Describe the first stage of labour
The time between the onset of regular contractions, until the cervix is fully dilated
Latent phase is when the cervix is less than 4cm dilated, and not yet fulled effaced
Active phase is between 4-10cm dilated and cervix is fully effaced
What is effacement
The change in the shape of the cervix from ‘bulbed’ to flat
- balloon demonstration
Describe the second stage of labour
Between complete dilation of the cervix, and birth of the baby
- normally takes between 15-120 mins
Describe the third stage of labour
Delivery of the placenta and membranes
- control of bleeding
Describe the mechanisms of labour
Engagement (in the occipito-transverse position, the fetal head entered the pelvis)
Decent and flexion of the head as it aligns with the pelvic gutter
Internal rotation occurs as the gutter forces the fetal head to turn 45 degrees, so the baby is facing posteriorly
- shoulders remain occipito-transverse
Extension of the fetal neck occurs as the head passes under the symphysis pubis, and the head is delivered
Restitution (external rotation) occurs once the head is delivered (occipito-anterior), and realigns with the shoulders (occipito-transverse)
Expulsion is delivery of the shoulder and rest of the fetus
- anterior shoulder first, then posterior
How is labour diagnosed
Regular painful contractions in the presence of an effaced cervix (which is 3cm or more dilated)
Contractions are identified by palpation and identification on CTG
Clinical assessment of labour
Palpation of contractions - strength - timing - length CTG - only information regarding the timings of contractions, not strength Vaginal examination - bishop's score - dilatation - effacement
What is a partogram
Composite graphical record of key data (maternal and fetal) during labour
Components
1) patient ID
2) time, recorded at intervals of one hour
3) fetal heart rate (every 30 mins)
4) state of membranes and colour of liquid
5) cervical dilation and decent of head
6) uterine contractions (duration and intensity)
7) drugs and fluids
8) blood pressure every 2 hours
9) pulse rate every 30 mins
10) oxytocin
11) urine analysis
12) temperature
What are the components of a Bishop’s score
- used for cervical assessment
Cervical dilatation Length of cervix Station of presenting part Consistency Position
The higher the score, the more likely labour will begin without induction
Differences between a pregnant and non-pregnant uterus
Non-pregnant - 6-8cm long - 5cm wide - walls 2cm thick - 70g Pregnant - cellular hyperplasia and hypertrophy - 4-5 x enlarged - 1000g - accommodates 5 litres
Describe the balance of forces that keep the fetus in-utero until term, and the balance of forces that allow delivery of the infant at term
Fetus kept in-utero because - high cervical resistance - low muscular corpus expulsive forces Fetus delivery because - low cervical resistance - high muscular corpus expulsive force
Describe the differences between the uterine cervix and the uterine corpus
Uterine cervix - sparse contractile myocytes - high fibrous connective tissue (provides tensile strength) - type 1 and type 3 collagen Uterine corpus - parametrium - myometrium (muscle) - endometrium (ciliated columnar epithelium)
Describe the myometrium
Provides the tissue which allows the uterus to contract
- mainly myocytes
- also connective tissue, blood vessels, lymphatic vessels and nerves
What are the two main hormones that modulate contractile activity
Oxytocin
Prostaglandin
What is oxytocin used for in labour
IV infusion of synthetic oxytocin is used to induce labour by stimulating contractions
After amniotomy
Risk of tonic contraction
What are prostaglandin, and how are they used in labour
They are uterotonic and cervical priming hormones
Shown to ripen the cervix when applied topically during the inducation process
Endogenous prostaglandin can also stimulate myometrial contractility
Risk of uterine hyperstimulation
What is tocolysis
In pre-term labour, attempts at reversal of uterine activity can be made
- this is mainly to allow the administration of steroids, which aid the development of fetal lung maturation
- may also allow transfer to another hospital that offers neonatal care
No method has been proven safe
- none show an improvement in neonatal mortality or morbidity
Which tocolytic agents are used in clinical practice
Beta-agonists e.g. ritodrine
- most common agent in UK
acts on beta-receptors in myometrium to cause relaxation
- SE of pulmonary oedema can be fatal
Calcium-channel blockers e.g. nifedipine
- blocks calcium channels in the myometrium, interrupting contractions
- may alter uteroplacentral blood flow
Oxytocin receptor antagonists e.g. atosiban
- delays delivery with the least SE for mother and fetus
- very expensive
Magnesium Sulphate
- Competes at calcium channels in the myometrium
- linked to increased neonatal mortality
NSAIDs e.g. indomethacin
- acts on the COX enzyme that catalyses prostaglandin production
- drug with highest SE for fetus
Definition of pre-term birth
Birth occuring at <37 completed weeks gestation
Risk factors for pre-term birth
Maternal stress Maternal BMI Maternal age Antepartum heamorrhage Socio-economic status Alcohol/cigarettes/recreational drugs Maternal infection Maternal ethnicity - afro-caribbean Family/personal history Multiple pregnancy
Complications of pre-term birth
Respiratory distress syndrome Transient tachypnoea Chronic lung disease Pneumonia Apnoea and bradycardia Infection Jaundice Intraventricular haemorrhage Inability to maintain body heat Immature GI system Inguinal hernia Anaemia Patent ductus arteriosus Retinopathy of prematurity Necrotising Enterocolitis Sepsis Developmental diability Cerebral palsy UTI
Describe the role of steroids in the management of pre-term delivery
Corticosteroids can be administered in order to boost fetal lung surfactant producation and therefore reduce fetal respiratory distress
- two IM injections 12 hours apart
Recommended in women in threatened pre-term labour between 24 and 36 weeks gestation
Define a postdates pregnancy
Pregnancy after 40 weeks gestation (after then estimated date of delivery)
Post-term
- pregnancy after 42 weeks gestation (EDD +14 days)
