1st Stage of Labour Flashcards
What is the definition of labour?
The process by which the fetus, placenta and membranes are expelled through the birth canal
When is the onset of labour normally expected?
Between 37 and 42 weeks gestation or 280 (+/- 10) days
What is the definition of the first stage of labour?
From the onset of regular contractions to complete dilation of the cervix
Do colagen levels in the cervix increase or decrease at the onset of labour and what causes the change?
Decrease caused by an increase in collagenase
Do most cervixes ripen before or after the onset of contractions?
Before
What is effacement?
The process by which the cervical canal is drawn up into the lower segment of the uterus and the cylindrical cervix becomes funnel shaped
What is cervical dilation?
The enlargement of the cervical os from a closed point to an opening wide enough to allow the widest diameter of the presenting part to pass through
What document is the progress of the labour noted on?
Partogram
What happens once the cervix is stimulated?
It promotes oxytocin release which stimulates uterine contractions and therefore prostaglandin are released.
Name the THREE layers of pregnant uterus
- Inner layer is the decidua
- Middle layer is the myometrium
- Outer layer is the perimetrium
How does oestrogen affect the muscle fibres during pregnancy?
Fibres increase in length (hyperplasia) and in size (hypertrophy)
How far apart and how long lasting are early labour contractions?
15-20 minutes apart
Lasts around 30 second
How far apart and how long lasting are established labour contractions?
3-4 times every 10 minutes
Lasts 50-60 seconds
What is intrauterine hydrostatic pressure?
The pressure exerted on the amniotic fluid by the contractions
What is the resting pressure exerted by the myometrium?
5 mmHg (millimetres of mercury)
What is the pressure of the myometrium in pregnancy?
Up to 30 mmHg (millimetres of mercury)
What is the pressure of the myometrium in labour?
60-80 mmHg (millimetres of mercury)
What does polarity mean during contractions?
The upper and lower poles of the uterus act in harmony, with contraction and retraction of the upper pole and dilatation of the lower pole to allow expulsion of the fetus
What is retraction?
The progressive shortening of the uterine muscle fibres.
The muscles contract during a contraction but instead of fully relaxing, they retain some of the shortening.
What leads to the progressive shortening and thickening of the upper uterine segment?
Retraction
What is a retraction ring?
A physiological ridge which forms between the upper and lower segments of the uterus
What is the operculum?
The mucous plug located in the cervical os, formed in pregnancy
What is the technical definition of a “show”
The discharge of the operculum which may be blood stained owing to the rupturing of some capillaries when the lining of the cervix is stretched or where the chorion has become detached from the dilating cervix
What are forewaters?
A small sac of amniotic fluid, trapped between the head and the cervix following increased uterine pressure
What are hindwaters?
The amniotic fluid that is not trapped between the head and the cervix
What is meant by general fluid pressure?
The distribution of equal pressure from the contractions, throughout the amniotic fluid