Labour and Delivery Flashcards
What does expulsion of the foetus require
Creation of birth canal
Release of structures which normally retain the foetus in utero
Enlargement and realignment of the cervix and vagina
Explusion of the foetus
Expulsion of the placenta and changes to minimise blood loss from the mother
What does ‘the lie of the foetus’ mean and what is the commonest ‘lie’
Lie of the foetus describes the relationship of the long axis of the foetus to the long axis of the uterus
Commonest lie is longitudinal lie with head or buttocks posterior
What does presentation of the foetus mean
Presentation of the foetus describe the part of the foetus adjacent to the pelvic inlet
If baby lies longitudinally, presenting part might be cephalic or podalic
Presenting part may be in variety of positions which affects diameter of presentation
What is the common presentation of the foetus at birth
Foetus lies longitudinally in a cephalic presentation
It is well flexed so the vertex presents to the pelvic inlet
How is the birth canal formed
Birth canal is formed by the pelvic inlet
Softening of pelvic ligaments allows some expansion of the pelvis to allow for movement through
Cervix dilates and retracts anteriorly to form the canal
Softening of the pelvic ligaments also softens other ligaments, which ligaments are primarily affected and what does this cause
Vertebral ligaments are relaxed as a result of pelvic ligament softening - caused by relaxin
This causes a lumbar lordosis and a waddling gait
What is cervical ripening and why does it occur
Cervical ripening involves decreased collagen and increased glycosaminoglycans which causes decreased aggregation of collagen fibres -> collagen bundles loosen
Cervical ripening is triggered by prostaglandins
Cervical ripening helps to cause cervical dilatation
What happens to the myometrium during pregnancy and what contractions are felt as pregnancy continues (what is the name of the contraction)
Myometrium thickens during pregnancy due to increased cell size and glycogen deposition
Braxton-Hicks contractions are felt becuase there is increased amplitude of contractions as pregnancy continues
What happens to contractions at the onset of labour and what hormones cause this change
At onset of labour, contractions increase in frequency and force because of oxytocin and prostaglandins
Prostaglandins - enhance release of Ca from intracellular stores
Oxytocin - lowers threshold for triggering action potentials
Oestrogen levels increase at labour to stimulate oxytocin receptor production to increase response by uterus to oxytocin
What reflex is initiated by increased number of contractions and what does this reflex do
Ferguson reflex
This reflex increases oxytocin secretion as sensory receptors in the cervix and vagina are stimulated by contractions which then send signals to hypothalamus promoting large oxytocin release
What is brachystasis, what tissue is affected by brachystasis during labour and how does this help delivery
Brachystasis is where at each contraction, muscle fibres shorten but do not relax fully
This occurs in uterine smooth muscle during labour and so it shortens the uterus progressively
This helps push the presenting part into the birth canal
When does the first stage of labour end, when does the second stage end and when does the third stage end
First stage ends when cervical dilatation reaches 10cm
Second stage ends with delivery of the foetus
Third stage ends with expulsion of all other parts of pregnancy that remained in the uterus after the second stage
What happens in the second stage of labour/delivery of foetus
Descended head flexes as it meets the pelvic floor to decrease diameter of presentation
There is sharp internal rotation
The sharply flexed head then descends to the vulva then stretches the vagina and perineum
The head is delivered and as it emerges it rotates back to its original position and extends
Shoulders rotate, followed by the head
Shoulders are delivered, followed rapidly by rest of the foetus
What happens during the third stage of labour
Powerful uterine contractions separates the placenta and positions it in the upper part of the vagina/lower uterine segment
Placenta and membranes are then expelled
Contraction of uterus helps to compress blood vessels to reduce bleeding
What substances are given to help with labour
Prostaglandins to help induce labour
Oxytocin given during third stage to enhance uterine contraction and help prevent bleeding
