20) Parturition Flashcards
What is parturition?
Giving birth
What is spontaneous abortion?
Expulsion of products of conception before 24 weeks
What is pre-term birth?
Expulsion of products of conception between 24-36 completed weeks
What is term birth?
Expulsion of products of conception between 37-42 weeks
What is post-term birth and its clinical significance?
Expulsion of products of conception after 42 weeks
Pregnancy induce prior to this as fetus and mother at risk
Generally describe the 3 stages of labour:
1st: creation of birth canal
2nd: expulsion of fetus
3rd: expulsion of placenta and contraction of uterus
When does the uterus become palpable?
12 weeks
What is the lie of the fetus? (state the normal lie)
Its long axis in relationship to the long axis of the uterus Usually longitudinal (head or buttocks facing inlet)
What is the presentation of the fetus?
Give examples:
Part adjacent to pelvic inlet
Crown of head (cephalic), buttocks (breech)
How is pelvic inlet diameter increased during pregnancy?
Collagenases soften ligaments
What soft tissue structures need expanding to create the birth canal?
Cervix, vagina and perineum
Describe the process cervical ripening:
Reduction in collagen of cervix by increases in GAGs and hyaluronic acid
What triggers cervical ripening?
Prostaglandins
How does myometrium change in labour?
Hypertrophy
Increased forced of contraction due to greater intracellular calcium by action potentials from pacemaker
Describe Braxton-Hicks contractions:
Prepare uterus for labour, slightly high amplitude but less frequent than ‘real contractions’
Describe the contractions in labour:
Early - variable with high amplitude
Late - more frequent and high amplitude
How is clinical labour defined?
Contractions that last for longer than a minute and 3 within 10 minutes
Where are prostaglandins in the uterus produced?
Myometrium and decidua
How do the sex steroids affect prostaglandin production?
Higher oestrogen:progesterone ratio = more prostaglandins
What is the effect of prostaglandins and oxytocin of uterine contractions?
More forceful due to prostaglandins
More frequent by oxytocin
What is the effect of the sex steroids on oxytocin?
Higher oestrogen:progesterone ratio = more oxytocin receptors on SM
What is the Ferguson Reflex?
Positive feedback from cervix and vagina in response to uterine contraction, which causes more oxytocin release and more prostaglandins, further increasing force and frequency of contractions
What is brachystasis?
Uterus relaxes less than it contracts so fibres gradually shorten, pushing presenting part of baby into birth canal
Describe the movements the fetus makes during delivery:
Flexes head when it meets pelvic floor, then head rotates internally
Head delivered so rotates externally and extends
Shoulder rotates before delivery
