Labour Flashcards
How many weeks of gestation is defined as “term”?
37-41
What are the the boundaries of “pre-term” and “very pre-term” delivery?
Pre-term: 22-37 weeks
Very pre-term: 28-32 weeks
What moderates the cervical changes that occur in labour?
PGE2
IL8
MMPs
What moderates the myometrial contractions occurring in labour?
PGE2
Oxytocin receptor upregulation
Contraction associated proteins increased
Where is PGE2 produced in labour?
Foetal membranes
Describe the changes in the foetal membranes during labour
Foetal membranes rupture
Inflammatory process occur, + FMs secrete PGs, ILs + MMPs
What can up-regulate inflammatory pathways in fetal membranes, and thus are candidate initiators of term labour?
CRH + PAF upregulate pro-inflammatory cytokines
Progesterone loses its anti-labour effects at term
Summarise how progesterone loses its anti-labour effects at term
NF-KB levels rise, progesterone receptor levels fall
Free NF-KB drives pro-labour processes
What is the role of NFKB in labour?
Involved in pro-inflammatory processes, upregulates cytokines, oxytocin + PG receptors
Describe the epithelial changes in the foetal membranes during labour
Amnion epithelium on BM loses strength
What 2 processes are undergone by the cervix in labour?
Effacement: softer + flexible
Dilatation: thinner + stretched sideways
What must happen in order for cervical effacement and dilatation to occur? What accelerates this process?
Excessive ECM remodelling
Increasing pressure of fetal head on cervix due to increasing strength + frequency of myometrial contractions
Recall the key mediators in uterine contraction in labour
PGE2 from foetal membranes
Oxytocin receptor
How long does the onset of uterine contraction last in labour?
~8 hours
When do foetal membranes usually rupture?
During onset of labour
What is the 2nd stage of uterine contraction, and how long does it last?
Expulsive effort
~30 mins
Name the 3 stages of labour
- Cervical ripening + effacement + onset of myometrial contraction
- Complete cervical dilation + expulsion of infant
- Expulsion of placenta
How long should the 3rd stage of labour last?
30 minutes
Summarise the non-haematological events of the 3rd stage of labour
Uterus contracts very powerfully to expel placenta, causing a rupture between uterus + placenta –> delivery
What conditions are required in the spiral arteries in order to achieve successful haemostasis in placental delivery
High flow + low pressure
How does the myometrium control haemostasis following placental delivery?
Contracts forecefully
What is involution and what drives it?
Powerful myometrial contraction that causes haemostasis of spiral arteries (stops flow)
Driven by oxytocin (contractile hormone)
Summarise the hypothesis for parturition
CRH increase
Foetal adrenal stimulated, produces cortisol
Positive feedback in placenta between CRH + cortisol
Cortisol drives IL, PG + PAF production = pro-labour factors
What is labour?
Final stage of pregnancy
Expulsion of fetus + placenta from the uterus
What are the key tissues involved in labour?
Cervix
Myometrium
Foetal membranes
What factors may predispose to labour?
Anything increasing CRH levels e.g. stress
Anything increasing muscle contraction e.g. excess stretch of uterus
Anything activating inflammatory cascades e.g. infection
How is the cervix assessed before the onset of labour?
Bishop’s score: predicting whether induction of labour will be required + likelihood of spontaneous preterm delivery
Manual vaginal examination:
Cervical dilation in cm
Cervical effacement as %
Cervical consistency
Cervical position
Foetal station: position of foetal head in relation to pelvic bones
“Call PEDS For Parturition! = Cervical Position, Effacement, Dilation, Softness; Foetal Station”
