9. Principles of Labour And Delivery Flashcards by Shadekiel Kassie

What is the first phase of labour

Contractions: Regular Uterine activity

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What is the Second Phase of Labour?

Progressive effacement (shortening) and dilation (opening) of the cervix

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What is the last stage of labour

Expulsion of the products of conception POC

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What is the embryonic origin of the uterus

Paramesonephric ducts

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What is the weight of the uterus in the nulliparous woman

60-80g

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What are the four parts of the uterus

Fundus, body, isthmus and cervix

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What are the three payers of the uterus

Endometrium
Myometrium
Peritoneum

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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)

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Define Immune Tolerance

It is the process by which both cell mediated and, to a lesser extent, humoral immunity are reduced

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What is the result of failure of Immune Tolerance

Pregnancy loss

Pre eclampsia

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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

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The Gravid Uterus increases in length from 7-8cm to ______

36-40cm

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The Gravid Uterus increases in weight from 60g-80g to _______

850-950g

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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

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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

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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

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Which hormones are thought to be the triggering event in initiating labour

Corticotrophin releasing hormone CRH

Cortisol

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Which structures produce CRH and Cortisol to initiate labour

The fetus and the placenta

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Which hormones are termed the placental clock

CRH (corticotrophin Releasing Hormone)

Cortisol

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How does CRH and Cortisol release from fetus and placenta affect estrogen release from the placenta

Increases production of estrogen

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What is the effect of estrogen on the uterine muscle during labour

Reduces the inhibition of the uterine muscle by progesterone

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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

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What is the effect of estrogen on actin and myosin in uterus in prep for labour

Increases them

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What is the effect of estrogen on oxytocin receptors in the uterus in prep for labour

Upregulation

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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