Obstetrics - normal labour Flashcards
What are the borders of the pelvic inlet?
Posterior - sacral promontory
Lateral - Iliopectineal line
Anterior - pubic symphysis
What are the borders of the pelvic outlet?
Posteriorly: Tip of the coccyx
Laterally: Ischial tuberosity
Anteriorly: Pubic arch
What are the key stages of labour?
- Descent
- Engagement
- Neck flexion
- Internal rotation
- Crowning
- Extension of the presenting part
- Restitution /External rotation
What causes descent of the baby through the pelvic inlet?
Uterine contractions
Amniotic fluid pressure
Abdominal muscle contraction
When does descent usually occur?
From 38w onwards in 1st pregnancy, in a multigravida woman it may not occur until labour is established
What is engagement?
When the largest diameter of the foetal head fits into the largest diameter of the maternal pelvis
What happens in flexion?
The occiput of the foetal head comes into contact with the pelvic floor causing flexion.
This causes the foetal skull to have a smaller diameter
What causes internal rotation (first one)?
The pelvic floor has a gutter shape with a forward and downward slope encouraging the foetal head to rotate 90 degrees into an occipital anterior position
What is the clinical sign showing that the baby is crowning?
When the widest diameter of the fetal head successfully negotiates through the narrowest part of the maternal bony pelvis, the fetal head is considered to be ‘crowning’.
This is clinically evident when the head, visible at the vulva, no longer retreats between contractions.
What is the woman encouraged to do once the baby starts crowning?
Complete delivery of the head is imminent and so often the woman is encouraged to pant so that the head of the baby is born with control.
What is restitution?
When the foetus naturally aligns its head with the shoulders once the head is born.
You may see the head externally rotate to face either the right or left medial thigh of the mother
