Labour and birth Flashcards
Define labour
- Process by which foetus and supporting placenta pass from uterus to outside world
- Regular uterine contractions result in thinning and dilation of cervix
- Allows products of conception to leave uterus
What are the 3 key processes of labour?
- Regular high intensity contractions
- Softening and dilation of cervix
- Rupture of foetal membranes
What triggers labour?
- Mechanical
- Hormonal
- Prostaglandins
- Neurological
What is labour called at different stages of pregnancy?
- If expulsion of foetus and placenta occurs after 24 weeks of gestation = labour
- Before 24 weeks = miscarriage/parturition
- Labour that occurs before 37 weeks of gestation = premature/preterm labour
What are the 3 stages of labour?
- From onset of established labour (regular uterine contractions) until cervix is fully dilated
- From full dilation until foetus is born
- From birth of foetus until placenta and membranes are delivered
Outline what happens in the first stage of labour
- Creation of birth canal
- Release of structures which normally retain foetus in uterus
- Enlargement and realignment of cervix and vagina
Outline what happens in the second stage of labour
- Expulsion of foetus
Outline what happens in the third stage of labour
- Expulsion of placenta
- Changes to minimise blood loss from mother
What are the different phases of the first stage of labour?
- Latent phase (uterus prepares to contract)
- Active phase - consists of acceleration phase, phase of maximum slope, deceleration phase
What does the clinical management of labour crucially depend on?
- Lie, presentation and position of foetus
What is meant by the lie of the foetus?
- Relationship of long axis of foetus to long axis of uterus
- Commonest lie is longitudinal with head or buttocks posterior
What is meant by the presentation of the foetus?
- What part of foetus is adjacent to pelvic inlet
- If baby lies longitudinally, presenting part may be head (cephalic) or breech (podalic)
What happens if the baby is lying transversely?
- Can’t be delivered vaginally
What is the presenting part of the foetus?
- Portion of foetal body that is either foremost in birth canal or in closest proximity to it
How do we determine foetal position?
- Obstetric examination - can feel curvature of spine and determine where baby’s head is
- Vaginal examination - can palpate baby’s head and feel suture lines to work out which way baby is facing
What are the different types of breech position?
- Complete breech - legs crossed
- Frank breech - legs extended up
- Footling breech - dangerous because foot can come out before cervix is fully dilated and lead to cord prolapse
What determines the limits of the birth canal?
- Pelvis
- Diameter is 11cm max
What allows the creation of the birth canal?
- Softening of pelvic ligaments may allow some expansion
- Increase in myometrial activity (contractions)
- Cervical dilation and effacement
What must happen to the cervix to create a birth canal?
- Dilate - facilitated by structural changes called cervical ripening
- Produced by forceful contractions of uterine smooth muscle
- First thin cervix (effacement) and then dilate it
- Retracted anteriorly
What changes occur at a cellular level to allow cervical ripening?
- Cervix has high connective tissue content made up of collagen fibres embedded in a proteoglycan matrix
- Ripening involves marked reduction in collagens
- Plus marked increase in glycosaminoglycans
- Causes collagen bundles to loosen
- Influx of inflammatory cells
- Increased nitric oxide output
- Triggered by prostaglandins (E2 and F2a)