Labour and Delivery Flashcards
Define parturition
Transition from being preg to non-preg state
Define labour
Physiological process by which fetus is expelled from uterus to outside world
Define delivery
Method of expulsion of fetus, transforming fetus to neonate
What are the stages of labour?
First stage = creation of birth canal
Second stage = descent, rotation, delivery
Third stage = placental delivery
Outline the first stage of labour
Contractions begin
Descent of fetal head into birth canal
Creation of birth canal
1) latent phase = slow cervical softening, shortening, opening
2) active phase = faster rate of change, regular contractions
Outline the second stage of labour
Fetal head descent and rotation through the dilated cervix, birth canal and delivery
1) passive phase = descent and rotation
2) active phase = maternal effort to expel the fetus and achieve birth
Outline the third stage of labour
Delivery of placenta
Usually 5-15 mins
How does labour get initiated?
Rise in oestrogen:progesterone ratio
Prostaglandins = initiate softening of cervix, maintain/initiate uterine contractions
Oxytocin = uterine contractions
Outline the functions of prostaglandins
Induce cervical ripening
Induce cervical contractions
Increase myometrial sensitivity to oxytocin
Raise intracellular Ca = myometrial cell contract
Enhance myometrial gap junctions = strengthen contractions
What is cervical ripening?
The changes in the cervix when labour is being initiated
1) reduction in collagen
2) increases in GAGs
3) increase in hyaluronic acid
4) reduced aggregation of collagen fibres
Due to oestrogen, relaxin and prostaglandins breaking down the connective tissue
Where are prostaglandins produced?
Mainly in myometrium and decidua
Increased synthesis by amnion in third trimester
Released from cervical stretching
How does progesterone effect contractions?
Inhibits
Relative fall in progesterone = facilitates myometral excitability
Where is oxytocin secreted from and how is it controlled?
Secreted by posterior pituitary
Controlled by hypothalamus = +ve feedback from cervix and vagina (Ferguson reflex)
What is the role of oxytocin?
Initiates uterine contractions
Increases prod of prostaglandins which increase the contractions further
What increases the number of oxytocin receptors?
Oestrogen
Define cervical effacement
Thinning of the cervix = cervical ripening
What is the normal diameter of the birth canal?
9.5cm
Max size determined by the pelvis but softening of ligs may increase it
Outline how the pelvic floor, vagina and perineum change during labour
stretching of the fibres of the levator ani and the thinning of the central portion of the perineum transforms to almost transparent membranous structure
Describe the contraction of myometrium during labour
Contracts but only partially relaxes = doesn’t return to original size
Contraction from 2 poles – then fundus – then lower segment
Forces in upper segment more powerful than lower segment
How can the fetus lie?
Longitudinal
Transverse
Outline the positions of altitude the fetus can be in
Flexion = head, arms, leg flexed tightly against trunk
Extension = head, arms, legs extended
Outline the different presentations of a fetus
Frank breech = bottom first, legs extended
Full breech – bottom first, legs flexed
Single footling breech = bottom and one leg first
How is labour induced?
Stimulate release of prostaglandins – membrane rupture
Artificial prostaglandins
Synthetic oxytocin
Anti-progesterone agents
How can the physiology be monitored during labour?
Heart rate
Maternal temp
Doppler
Colour and amount of amniotic fluid
Scalp capillary pH
Outline the mechanism of labour
Head flexes = present minimum diameter
Head rotates internally = hits levator ani which contracts and rotates it (head tucked under and facing backwards)
Head crowns = stretches perineal muscle and skin
Extension of head and external rotation
Shoulder rotate, shoulders delivery – followed rapidly by body
How can delivery be facilitated?
Cesarean section
Forceps
Vacuum extraction
Describe the separation and descent of the placenta
Baby born = reduced uterus size
Inelastic placenta squeezed by contraction
How is bleeding controlled?
Powerful contractions of uterus = constrict blood vessels through myometrium
Pressure on placental site by wall of contracted uterus
Blood clotting
Describe the control of milk let down
Suckling = activation of mechanoreceptors = up spinal cord to hypothalamus = 1) on signal to PP to prod oxytocin, 2) off signal to AP to stop prod dopamine, which allows prolactin to be secreted
Prolactin = milk fat synthesis
Oxytocin = stim myoepithelial cell = milk ejection
Describe the mechanism which produces cessation of lactation
Mother stops breast feeding
Reflex that cause milk let down is lost = lactation ceases
Describe the structure of a normal breast
Alveolus = milk secretion
Ductule = connecting alveolus to duct
Duct = feeds to lactiferous sinus – exits via nipple pore
Ampulla = sac
Areola = pigmented region around nipple
Order the cardinal movement of labour
engage flexion of the neck rotation extension of the neck restitution delivery of anterior shoulder delivery of posterior shouder
What does the first stage of labour end with?
Ripening = pull dilation of the cervix
What is the most common cause of post-partum haemorrhage?
uterine atony = uterus fails to contract after delivery
What hormonal change is responsible for secretion of milk after delivery?
decreased progesterone and oestrogen
