9. Principles of Labour And Delivery Flashcards
What is the first phase of labour
Contractions: Regular Uterine activity
What is the Second Phase of Labour?
Progressive effacement (shortening) and dilation (opening) of the cervix
What is the last stage of labour
Expulsion of the products of conception POC
What is the embryonic origin of the uterus
Paramesonephric ducts
What is the weight of the uterus in the nulliparous woman
60-80g
What are the four parts of the uterus
Fundus, body, isthmus and cervix
What are the three payers of the uterus
Endometrium
Myometrium
Peritoneum
Describe the layers of the muscle fibres of the myometrium of the uterus
Deep- circular layer
Superficial- Longitudinal layer
( majority of the fibres run obliquely, in an interlacing fashion)
Define Immune Tolerance
It is the process by which both cell mediated and, to a lesser extent, humoral immunity are reduced
What is the result of failure of Immune Tolerance
Pregnancy loss
Pre eclampsia
What causes Anatomical Tolerance in Pregnancy
Progesterone produced by the placenta, causes relaxation of the uterine muscle
NB// a hollow viscera which becomes occluded and distended tends to automatically contract in an effort to clear the obstruction….the progesterone secretion prevents this from happening in pregnancy until full term
The Gravid Uterus increases in length from 7-8cm to ______
36-40cm
The Gravid Uterus increases in weight from 60g-80g to _______
850-950g
List six main changes in the gravid uterus
Increases in length Increases in weight General thickening of the ligaments supporting the uterus Blood vessels enlarged Gap junctions develop Hyperplasia and hypertrophy
What is the significance of the development of gap junction in the Gravid Uterus
They allow changes in membrane potential to spread rapidly from one cell to another facilitating depolarization and synchronous contractions
What is the function of the functional linkage of the myometrial cells during labour
Allows the pacemaker activity of the uterine fundus to promote the co ordinated, fundal dominant contractions necessary for labour
Which hormones are thought to be the triggering event in initiating labour
Corticotrophin releasing hormone CRH
Cortisol
Which structures produce CRH and Cortisol to initiate labour
The fetus and the placenta
Which hormones are termed the placental clock
CRH (corticotrophin Releasing Hormone)
Cortisol
How does CRH and Cortisol release from fetus and placenta affect estrogen release from the placenta
Increases production of estrogen
What is the effect of estrogen on the uterine muscle during labour
Reduces the inhibition of the uterine muscle by progesterone
List five effects of Estrogen on uterus in preparation for labour
Reduces the inhibition of uterine muscle by progesterone
Upregulates oxytocin receptors
Increases the number of gap junctions between smooth muscle cell
Increases actin and myosin which are the proteins needed for contraction
It also increases the production of prostaglandins
What is the effect of estrogen on actin and myosin in uterus in prep for labour
Increases them
What is the effect of estrogen on oxytocin receptors in the uterus in prep for labour
Upregulation
Which hormone is responsible for “ripening” of the cervix (softening and shortening )
Prostaglandins
Prostaglandins causes an increase in production and activity of which enzymes
Collagenase Elastase Hyaluronidase Matrix Metalloproyeinases
What is the effect of increases in Collagenase, Elastase, Hyaluronidase, Matrix, Metalloproyeinases on the uterus
Ripens the cervix
Softening and shortening of the cervix
Which hormone is mainly responsible for uterine contractions
Oxytocin
How do we know that oxytocin is responsible for uterine contractions
An increase in the number of oxytocin receptors in the uterine muscle
Increased secretion by the posterior Pituitary
Positive feedback to posterior pituitary via stretching of cervix
True or False
Sensitivity to Oxytocin increases with gravidity
True
Because the number of oxytocin receptors never go back to normal after pregnancy
Define Labour
Regular uterine activity (contractions), leading to progressive effacement and dilation of the cervix, and culminating in the expulsion of the products of conception
Where do uterine contractions start
At a pacemaker located at the junction between the fallopian tubes and uterus
Describe the path contractile waves in the uterus
Inwards and downwards to involve the entire uterus
In a normal labour where is the intensity of the contraction greatest
In the upper uterine segment as the muscle is thicker
Why is the intensity of the contraction greatest in the upper uterine segment
The muscle is thicker and there is greater amount of actinomyosin to contract
What is the formula for measuring uterine activity
The intensity of the contraction x the frequency of the contraction (per ten minutes)
Measure of uterine activity is expressed in which inits
Montevideo units
True or False
In a normal labour the intensity and frequency of the contractions increase but there is no increase in resting tone
True
In late labour, what value does the intensity increase to
60mmHg
In late labour what is the frequency of contractions
3-5 contractions every 10minutes
What is the measurement of uterine activity in Montevideo units
150-200 Montevideo units
What is the average duration of contractions in early labour
20secs
What is the average contraction duration in late labour
40-60secs
Which events lead to the descent of the fetus through the birth canal
The progressive shortening of the uterine muscle coupled with the progressive dilatation of the cervix
When does descent / engagement occur in primigravidas
36-37 weeks
When does descent / engagement occur in multigravidas
After onset of labour
What is meant by the term engagement
Widest part of the fetal head has entered the pelvis
What is the flexion position of the head of the fetus
Fetal head flexes to the chin to chest position
What aspects of the uterus lead to internal rotation of the fetal head
Funnel shaped pelvic floor
Uterine contractions result in a torsional force in the head causing it to rotate
What are the six mechanics of labour
Descent Flexion Internal Rotation Extension External Rotation Delivery
Explain the Extension Mechanics of Labour
After the head crowns, delivery is accompanied by extension of the neck
Describe external rotation in mechanics of labour
The fetal shoulders have reached the pelvic floor
Torsional forces again turn the infant, to allow the anterior shoulder to pass below the pubic symphysis
How many stages of labour are there
Three
Stage I
Stage II
Stage III
Define stage I labour
Beginning of labour to full dilatation
Which stage of labour is described as
the Beginning of labour to full dilatation
Stage I
What are the two phases of labour
Latent phase
Active Phase
What is the dilation measurement in the latent phase of stage I labour
3-4cm dilated
What is the dilation measurement in the active phase of stage I labour
4cm to fully (10cm) dilated
Describe Stage II labour
Full dilation to delivery of the infant
Describe Stage III labour
Delivery of the infant to delivery of the placenta
What are the three factors that affect the time spent in each stage of labour
Parity
Size of mother / fetus
Presentation / position of fetus
What is the time spent in Stage I latent phase
Variable
What is the time spent in Stage I active phase in primigravidas
6-12 hrs
What is the time spent in the active phase of Stage 1 in multigravidas
6-8hrs
Define precipitate labour
When a labour is very quick and short, and the baby is born less than 3hrs after the start of contractions
What is the average time spent at Stage II labour in Primigravidas
2hrs
+1hr if epidural given
What is the average time spent at Stage II labour in Multigravidas
1hr
+1hr is epidural given
What is the average time spent at Stage III labour
30minutes
Patients are advised seek medical care when which two events occur when close to end term pregnancy
Sudden rupture of Membrane SROM
Contracting 2 per ten minutes
List five steps of postnatal care
Check for or repair Lacerations
Express uterus
Put infant on breast as soon as possible
Monitor maternal vitals and vaginal blood loss
Mild analgesics for after pains