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25 Cards in this Set
- Front
- Back
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What is the biological term for labour
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parturition
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When is birth considered spontaneous abortion & premature
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spont abor - before 24 weeks
premature - before 37 weeks |
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Outline the 3 stages of labour
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1) creation of a birth canal - enlargement & realignment of cervix & vagina, up to dilation of 10cm
2) expulsion of foetus 3) expulsion of placenta & changes to minimise blood loss from mother |
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What does foetal 'presentation' refer to?
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the part of the foetus which lies at the pelvic brim or in the lower pole of the uterus
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Name the 5 presentations of a foetus
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- head (cephalic)
- breech (podalic) - shoulder - face - brow |
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What does the 'lie' of the foetus refer to?
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the relationship of the long axis to the uterus
(longitudinal = most common) |
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What is the most common lie & presentation of a foetus?
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Baby lies longitudinal in a cephalic presentation, well flexed so that the occiput presents to the pelvic inlet
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Describe the pelvic inlet boundaries that determine birth canal diameter
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posterior - sacral promontory
lateral - iliopectinal line anterior - superior pubic rami + upper pubic symphysis softening of pelvic ligaments allow some expansion |
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What happens when 'waters break'?
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foetal membranes rupture, releasing amniotic fluid, during cervical dilatation & anterior retraction
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What 2 things facilitate cervical dilatation?
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cervical ripening - structural changes
forceful contractions of uterine smooth muscle |
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Describe what occurs in cervical ripening
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Prostaglandins E2 & F2x trigger:
- marked reduction in collagen - marked increase in glycosaminoglycans - keratin sulphate increases Collagen bundles loosen, influx of inflammatory cells & increase in NO output |
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State 4 methods of labour induction
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- membrane sweep
- prostaglandins given vaginally - artificial rupture of membranes - oxytocin infusion |
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What are the 2 main types of foetal monitoring during labout?
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- intermittent
- continuous |
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Outline the suggested mechanism of labour initiation
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increase in prostaglandin production & oxytocin sensitivity triggered by a fall in progesterone levels relative to oestrogen
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Describe the coordination of myometrium contractions
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Myometrium is made up of smooth muscle bundles
APs in cell membrane increase intracellular Ca2+ which acts on actin & myosin to generate force APs spread across cells via gap junctions, allowing coordinated contractions to spread Some smooth muscle cells act as pacemakers - myometrium is spontaneously motile Braxton-Hicks contractions occur throughout pregnancy but are not forceful enough to expel foetus |
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What are Braxton-Hicks contractions?
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sporadic uterine contractions that sometimes start around six weeks into a pregnancy - low amp & freq
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Describe how 2 key hormones are implicated in the sudden increase in the frequency & force of myometrial contractions at the onset of labour
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prostaglandins - enhance release of Ca from intracellular stores
oxytocin - lowers threshold for triggering APs |
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From where are prostaglandins produced in labour & how is their synthesis promoted?
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Endometrium is a major prostaglandin producer - synthesis promoted when progesterone falls in relation to oestrogen
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Outline the positive feedback theory for the initiation of labour
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Increased prostaglandin release + increased oxytocin sensitivity = more forceful contractions
Ferguson Reflex - baby head stretches cervix - cervical stretch positively feeds back to pituitary - oxytocin release causes more forceful & frequent fundic contractions - stretches cervix further |
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Explain uterine smooth muscle brachystasis
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- at each contraction, muscle fibres shorted, but do not relax fully
- uterus progressively shortens - pushes presenting part towards birth canal - stretches/dilates cervix over it - first stage of labour ends when cervix fully dilated |
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How long does the 2nd stage of labour usually last?
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1 hour (multiparous women)
2 hours + (primigravida) |
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Outline the 2nd stage of labour - expulsion of the foetus (5)
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- head flexes
- internal rotation brings shoulders through pelvis - head descends & crowns - rotates back to original position & extends - shoulders rotate & deliver |
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Outline 3rd stage of labour
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powerful uterine contraction
- separates placenta - expelled - also compresses blood vessels & reduces bleeding enhanced by oxytocic drug |
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How is the condition of the neonate scored & what factors does this assess?
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Apgar Score
- colour - tone - pulse - respiration - response |
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Name 3 possible areas that problems may occur in labour. How is progression of labour plotted?
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Powers - myometrial contraction (low freq & amp)
Passage - formed by bony pelvis & soft tissues (resistance) Passenger - size & presentation of foetus (macrosomia) Progress in labour is plotted graphically on a partogram |
