Labour Flashcards
Describe the process of labour?
Fundally dominant coordinated contractions of myometrium accompanied by cervical ripening and effacement
Rupture of fetal membranes
Delivery of infant and placenta
Contraction of uterus
What is meant by cervical ripening?
Cervix changes from being rigid to soft and flexible as it widens
Why is it important that the placenta is delivered fully?
Because if it’s left in the uterus, it could cause a haemorrhage
What happens during the three stages of labour and how long do they last?
Phase 1 - contractions and cervical changes (many hours)
Phase 2 - delivery of baby (hours)
Phase 3 delivery of placenta (30 mins)
Describe the process of cervical ripening and effacement
Change form rigid to flexible structure
Remodelling of ECM
Recruitment of leucocytes
Release of inflammatory mediators
Which inflammatory mediators are released during cervical ripening and effacement?
PGE2
IL8
What kind of action does IL8 have in the cervix during labour?
Paracrine local effects
Name a leucocyte recruited during cervical ripening
Neutrophils
Describe the process of coordinated myometrial contractions
Dominant fundal contractions
Increased coordination and power of contractions
Release of more mediators
Increase in oxytocin receptors
Which mediators are released during coordinated myometrial contractions? State where they are released from
PGF2alpha (E2) - released from fetal membranes
Contraction associated proteins
What causes the fetal membrane to rupture?
Changes in amnion basement component causes loss of strength
What mediators are released from the rupture of fetal membranes?
Prostaglandins
Interleukins
Matrix-metaloproteinases
Describe the process of fetal membrane rupture
Amnion basement changes Loss of strength -> rupture Inflammatory changes Leucocyte recruitment Increased levels and activity of MMPs
Compare the inflammatory changes and leucocyte recruitment in normal labour vs preterm labour
These changes are modest in normal labour
Exacerbated in preterm labour
What is the target of many of the initiators of labour and what is the downstream effect?
NFkB - binds to promotor domains of prolabour genes and increases their activity
Also increases activity of inflammatory mediators
List some of the target genes of NFkB
COX-2 PGs, PG receptor IL8 IL1b MMPs Oxytocin receptor Contraction associated proteins
Give some supporting evidence for NFkB being involved in labour
Modification of NFkB sites in promotor sequences leads to loss of expression of genes
List some causes the initiation of labour during preterm
IU infection
IU bleeding
Multiple pregnancy
Maternal stress
Why does an IU infection cause preterm labour?
Release of inflammatory mediators
Increase in which three things are associated with term labour?
Increased CRH
Increased COX 2 synthesis
Increased PAF
Describe the downstream effect of increased maternal CRH in the mother, and in the fetus
In the mother: Increased PG Increased IL In the fetus: Increased ACTH
What is the downstream effect of fetal ACTH?
Stimulates release of fetal cortisol, which provides POSTIVE FEEDBACK on maternal CRH production
What else do fetal adrenals produce which help with parturition ?
Steroids
What is PAF and when is it produced?
Platelet activating factor - produced by maturing fetus lung before birth (it’s a part of lung surfactant)
What is PAF a sign of?
Fetal maturity
Where do PAF levels increase near term?
In amniotic fluid
What can predispose to labour/is seen in preterm labour?
Anything that increases CRH
Anything that increases muscle contraction
Anything that activates inflammatory cascades
Give examples of what may increase CRH levels
Stress
Multiple infants
Give an example of what may increase muscle contraction
Excess stretch of the uterus
What hormone is needed to maintain pregnancy?
Progesterone
How long do progesterone levels stay high for?
Until after delivery of the placenta
What happens to the effect of progesterone during labour, and how?
It is lost, due to overall decrease in progesterone receptor levels and change in the balance of progesterone receptors (from PR-B>PR-A to PR-A>PR-B during term)
What do you call this effect where progesterone levels remain high, but their effect is lost due to declining progesterone receptor levels?
Functional progesterone withdrawal
Which receptor mediates the effect of progesterone and how?
PR-B - via gene expression
Which progesterone receptor does not mediate the effect of progesterone very well?
PR-A
What is the consequence of decreased levels of progesterone receptors besides loss of progesterone effects?
Increase in free NFkB levels
