Flashcards in Labour and Delivery Deck (19):
What are pro-labour factors?
•Oestrogen (increased levels)
•Oxytocin (increased from posterior pituitary)
•Prostaglandins (chemical transmitters)
What causes the onset of labour?
Unknown, several theories: functional or actual decline of progesterone by the placenta at term
What are cervical and myometrial changes mediated by?
What cervical changes occur during labour?
Increased prostaglandin E2 and F2a in myometrium, decidual and foetal membranes --> prostagalndins promote cervical ripening and stimulate contractions (directly by acting on myometrium and indirectly by increasing oxytocin receptor expression)
What is 'cervical ripening'
Increased cervical distensability index (stretchier) through collagenolysis --> replaces collagen with amorphous substance
What myometrial changes occur during labour?
Prostaglandins develop cell-cell adhesion known as gap junctions and increase levels of oxytocin receptors
Describe the Ferguson's reflex
The development of a soft cervix which then stimulate the release of oxytocin from the posterior pituitary gland --> oxytocin binding to soft cervix receptors --> contractions (start at each corner and travel caudally)
What is Ferguson's reflex?
Name given to the neuroendocrine reflex comprising the self-sustaining cycle of uterine contractions initiated by pressure at the cervix or vaginal walls
Describe the signs of labour
Release of mucus plug (the show), rupture of amniotic membrane (waters breaking), painful contractions (if they come progressively closer together over a period of an hour or two and last longer than 40 seconds)
When is labour diagnosed?
When regular painful uterine contractions affect progressive cervical dilation
What are the three stages of labour?
Dilation of cervix from 0-10cm (uterine contractions), foetal expulsion and placental expulsion
Describe the first stage of labour
Cervix dilates at rate greater than 1cm/hour and normal Braxton-Hicks contractions become painful, rhythmic contractions every 2-3 minutes --> myometrial fibres contract and retract
Describe the second stage of labour
Contractions supplemented by voluntary contraction of abdominal muscles and fixing of diaphragm (increase in intra-abdominal pressure) and the foetus is delivered
Describe the third stage of labour
From delivery of the baby to placental expulsion, involves uterine muscles contracting tonically (constricts blood vessels between interlacing fibres), placenta separates as the placenta bed is constricted down to half it's size and expelled by uterine contractions
What does normal labour depend upon?
The passenger, passages and powers;
Passenger - foetus helps as it has a soft skull which allows it to fit through vaginal canal
Passages - birth canal shaped to allow the passage of the baby
What is another name for the birth canal?
Curve of Carus
What is the function of the pelvic floor?
Support pelvic viscera, help with continence, build up effective intra-abdominal pressure (alongside diaphragm and abdominal wall muscles), helps rotate the presenting part of the foetus
What is an episiotomy?
a surgical cut made at the opening of the vagina during childbirth, to aid a difficult delivery and prevent rupture of tissues.