Human labour and delivery Flashcards
How many miscarriages occur per annum within 13 weeks of gestation?
Around 350,000.
How many late miscarriages occur per annum?
Around 7000.
What is a miscarriage?
Loss of a pregnancy <23 weeks of gestation.
What is ‘term’ in pregnancy?
37-41 weeks of gestation.
What is ‘preterm’ in pregnancy?
23-37 weeks of gestation.
How many infants are born term per annum?
Around 700,000.
How many infants are born term by labour per annum?
Around 525,000 (75%).
How many infants are born term by elective Caesarean section per annum?
Around 175,000 (25%).
How many infants are born preterm per annum?
Around 80,000.
How many infants are born preterm by labour per annum?
Around 45,000.
How many infants are born preterm by emergency Caesarean section per annum?
Around 35,000.
What is labour?
Cervical ripening and effacement
Fundally dominant contractions
Foetal membrane remodelling
Lower segment relaxation
What are the processes of labour, independent of gestational age?
Cervical ripening and effacement (increasing)
Coordinated myometrial contractions (increasing)
Rupture of foetal membranes
Delivery of infant
Delivery of placenta
Contraction of uterus
How is labour initiated at term?
Not really sure.
Oestrogens, low progesterone? CRH? Oxytocin?
How is labour initiated preterm?
Intrauterine infection
Intrauterine bleeding
Multiple pregnancy
Stress (maternal)
Others
Describe the process of cervical ripening and effacement in labour.
Change from rigid to flexible structure.
Remodelling (loss) of extracellular matrix.
Recruitment of leukocytes (neutrophils).
Inflammatory process:
- prostaglandin E2, interleukin-8
- local (paracrine) change in IL-8
Describe the process of coordinated myometrial contractions in labour.
Fundal dominance.
Increased coordination of contractions.
Increased power of contractions.
What are the key mediators of coordinated myometrial contractions in labour?
Prostaglandin F2-alpha (E2) levels increased from foetal membranes.
Oxytocin receptor increased.
Contraction associated proteins.
Describe the process of rupture of foetal membranes in labour.
Loss of strength due to changes in amnion basement component.
Inflammatory changes, leukocyte recruitment- modest in normal labour, exacerbated in preterm labour.
Increased levels and activity of MMPs.
Inflammatory process in foetal membranes.
What are the main tissues involves in labour?
Cervix
Myometrium
Foetal membranes
What is NF-kappa-B?
Pro-inflammatory transcription factor thought to be involved in labour and inflammatory cascades- stimulates production of cytokines, chemokine, adhesion molecules and enzymes (e.g. COX-2).
What does NF-kappa-B regulate?
Many genes, mostly ‘inflammatory’.
COX-2 (prostaglandins).
IL-8.
IL-1-beta.
MMPs.
Oxytocin receptor.
Prostaglandin receptors.
Contraction associated proteins.
What is the supporting evidence for the involvement of NF-kappa-B in labour?
Almost all prolabour genes have NF-kappa-B binding domains in their promoters.
Modification of NF-kappa-B sites in promoter sequences leads to loss of expression in cells or in expression vectors.
What is platelet activating factor and its role in pregnancy/labour?
Part of lung surfactant.
Surfactant proteins and complexes.
Produced by maturing lung, before birth.
Levels in amniotic fluid increase near term.
Foetal signal of maturity.
What is the role of CRH and PAF in pregnancy/labour?
Can up-regulate inflammatory pathways in foetal membranes.
Candidate initiators of human term labour.
What factors may predispose to term labour?
Anything that increases CRH may predispose to labour (stress, multiple infants).
Anything that increases muscle contraction may predispose to labour (excess stretch of uterus).
Anything that activates inflammatory cascades may predispose to labour.
The above apply to preterm labour too (intrauterine infection, bleeding, twins).
What is the importance of progesterone in pregnancy?
Progesterone is NEEDED to sustain pregnancy.
Progesterone receptor blockade = pregnancy loss.
Progesterone levels remain very high until after delivery of the placenta.
Effect of progesterone lost in normal term labour.
What changes occur to progesterone receptors in pregnancy/labour?
PR-B mediates the main effects of progesterone via gene expression.
PR-A is less able to mediate these effects.
Ratio of PR-A:PR-B increases at term.
Loss or change in PR may lead to ‘functional progesterone withdrawal’.
