Labour Flashcards
Define term
37-41 weeks of gestation
Define pre-term, very pre-term, and extremely pre-term
pre-term: 23-37 weeks of gestation
Very pre-term: 28-32 weeks gestation
Extremely pre-term: <28 weeks
What is the definition of labour and what is it range of length
Fundally dominant contraction of the myometrium, coupled with cervical ripening and effacement
12-48 hours
Describe the process of labour
- Cervical ripening and effacement (increasing)
- Co-ordinated myometrial contractions (increasing)
- Rupture of fetal membranes
- Delivery of infant
- Delivery of placenta
- Contraction of uterus
What are the 3 phases of labour
Phase 1: Uterine contractions and cervical changes
Phase 2: Delivery of the of the foetus
Phase 3 (30 min) : Delivery of the placenta
What are the key tissues involved in labour
Cervix, myometrium (uterus) and foetal membranes
The foetal membranes are the fused chorion and amnion
What is effacement
The cervix undergoes changes to turn it from rigid to flexible
Effacement is shortening and thinning of cervical walls
What are the 3 mechanisms by which effacement occurs
Remodelling of the ECM
Leukocyte recruitment
Inflammation (PGE2 and IL8)
Describe uterine contraction during labour
co-ordinated myometrial contraction with fundal dominance
(uterus squeezed from top down)
Increased co-ordination and power
What are the key mediators of uterine contraction
Prostaglandin F2 alpha from foetal membranes
Oxytocin receptor activation
CAPs (contraction associated proteins)
What is ‘water breaking’ and why does it occur
Rupture of the foetal membranes
Rupture of these membranes happens due to inflammatory changes and membrane remodelling
What are the changes that occur during water breaking
Loss of strength due to changes to: The amnion basement component Leukocyte recruitment Increase in inflammatory processes Increased levels and activity of MMPs
What occurs in the third stage of labour
Placental delivery, there are some haemostatic changes that occur here to prevent maternal haemorrhage.
What are the haemostatic changes that occur in the third stage of labour
Increased clotting through pregnancy and powerful uterine contraction which will squeeze the maternal blood supply
What are the main biochemical factors involved in labour
NFkB
Progesterone and progesterone receptor
Corticotrophin releasing hormone (CRH) and platelet activation factor (PAF)
What is the role of NFkB in labour
The is a pro inflammatory transcription factor
Most pro labour genes bind NFkB domains to transcribe mediators involved in labour
What is the role of CRH and PAF in labour
PAF is a sign of fetal maturity made by the mature lungs which are the last to develop. It is part of lung surfactant.
CRH and PAF rise before labour and upregulate inflammatory pathways
What is the significance of progesterone in pregnancy
Progesterone is needed to sustain pregnancy - Progesterone receptor blockade leads to pregnancy loss
Progesterone levels remain very high until after delivery of the placenta
Effect of progesterone lost in normal term labour
What is the difference between the 2 types of progesterone receptor
PR B will mediate progesterone’s effects in pregnancy
PR A reduces its effects
At term PR A: B ratio increases, so you get progesterone withdrawal -> labour
What are the causes of pre-term labour
release of CRH, myometrial contraction and inflammation so anything that triggers these 3 factors will cause labour
Stress, twins = increase in CRH
Twins = increase in myometrial contraction
Intra-uterine infection, bleeding = inflammation
