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Flashcards in Physiology of 2nd Stage Deck (15)
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Describe the 2nd stage of labour

- Full dilation to birth
- Strong contractions every 2-3 minutes lasting 1 minute
- Foetus descends down birth canal


Name some of the features of the second stage of labour

- Increase contraction intensity
- Membrane rupture?
- Pressure of foetal head on sacral/ obsturator nerve
- Increased perspiration
- Stretch receptors stimulated
- Anus everted and patulous (open and spread out)
- Bulging of perineal region
- Dilated and distended vulva
- Rapid contractions with no interval
- Crowning
- Delivery


What are the primary and secondary powers?

Primary power = involuntary (contraction, retraction, relaxation)
Secondary power = urge to push


Describe crowning

Vulva stretches and encircles the largest diameter of the foetal head


What can delay labour?

Full bladder


What cardiovascular changes occur in the mother during 2nd stage?

- CO 40-50% up to 100%
- Compression of aorta and iliac arteries
- CO shifts to head and upper extremities
- BP increases by 30/25mmHg (during contraction) or 10/5mmHg (between contractions)
- Steady increase in PR to 100bpm


Why does cardiac output increase?

Increase in catecholamines resulting from pain


Give some reasons that pulse rate may increase

- Dehydration
- Anxiety
- Pain
- Some drugs


What is the most accurate period of assessment for vital signs?

Between contractions


What respiratory changes occur in the mother during 2nd stage?

- Increase in metabolism increases oxygen demand = increased RR
- PP of carbon dioxide decreases (32mmHg to 22mmHg)
- Hyperventilation common - leads to decreased PP of carbon dioxide
- Opposite effect occurs in excessive shallow breathing
- Excessive/prolonged maternal pushing causes decrease in oxygen


What gastrointestinal changes occur in the mother during 2nd stage?

- Decreased motility and absorption in active phase
- Delayed emptying time
- Exaggerated after narcotic intake
- Nausea and vomiting
- Dehydration, dry lips and mouth due to breathing deeply


What renal changes occur in the mother during 2nd stage?

- Full bladder may be masked by intensity of contractions and pressure of presenting parts
- May cause delayed progress/ trauma
- Diaphoresis (excessive sweating)
- Increased water loss through perspiration


What haematopoietic changes occur in the mother during 2nd stage?

- 500ml (usual loss)
- 1000ml (lost in CS)
- Compensated by hypervolemia
- Slight decrease in coagulation time
- Increased plasma fibrinogen levels
- Decreased leucocyte levels as labour progresses


What fluid and electrolyte changes occur in the mother during 2nd stage?

- Decrease in plasma Na and Cl levels due to decreased GI tract absorption, panting and diaphoresis
- Polyuria is common
- Analgesia may affect foetal electrolyte balance


What should be monitored in 2nd stage?

- Uterine contractions
- Cervical dilation
- Descent of presenting part
- Maternal wellbeing
- Foetal wellbeing