Define miscarriage
Delivery at <23 weeks gestation
Define term labour
Delivery at 37-41 weeks gestation
Define pre-term labour
Delivery at 23-37 weeks gestation
Define labour
Increasing fundally dominated contractions combined with cervical ripening and effacement
What does labour involve?
- Cervical ripening & effacement (increasing)
- Coordinated myometrial contractions (increasing)
- Rupture of foetal membranes
- Infant delivery then placental delivery
- Uterine contraction
Generally how long are the 3 phases of labour and what happens in each?
Phase 1 - many hours - contractions, cervical changes
Phase 2 - hours - baby delivered
Phase 3 - 0.5 hours - placenta delivered
What initiates labour during term?
Not entirely sure
May be high oestrogen: progesterone ratio, CRH or oxytocin
What can initiate labour pre-term?
- Intrauterine infection
- Bleeding
- Multiple pregnancy
- Maternal stress
What changes does the cervix undergo during labour?
Ripening & effacement:
- Change from rigid -> flexible structure
- Remodelling - loss of ECM
- Recruitment (leucocytes e.g. neutrophils)
- Inflammation (prostaglandin E2, IL-8)
What happens to the myometrium during labour?
Co-ordinated myometrial contractions:
- Fundal dominance with increased power and coordination
- Mediators: increased prostaglandin F2a, increased oxytocin receptors, contraction proteins
What happens to the foetal membranes during labour?
Loss of strength due to changes in amnion BM -> rupture
- Inflammation and leucocyte recruitment (exacerbated in preterm), increased MMPS (matrix metalloproteins)
What is NFkB?
Pro-inflammatory transcription molecule
- Closely related to IL1b, IL6, COX2, cPLA2, IL8
What does NFkB inititiate effects through?
COX2, IL8, MMPs, oxytocin receptors, PG receptors, contraction-associated proteins
What must be constitutively expressed before any changes conducive to labour can be seen?
PGE2
What factors control labour?
CRH & PAF -> activate other molecules and ultimately MMPs, PGE2 and upregulation of oxytocin receptors
What produces CRH?
Pituitary gland AND placenta
How do levels of CRH and CRH-binding proteins change towards the end of pregnancy?
CRH level: increase
CRH-binding protein: decrease
What is the relationship between CRH and COX2 expression?
High CRH correlates with high COX2 expression
What is PAF?
Part of lung surfactant that is produced by maturing lungs before birth
How do levels of surfactant and therefore PAF change as the foetus nears term?
Surfactant: increases
PAF: increases
What do CRH and PAF upregulate?
- PGE2 and COX2 expression
- IL1b levels
What are the three theories for labour induction?
- Anything that increases CRH may -> labour (stress, multiple infants)
- Anything that increases muscle contraction may -> labour (excess uterine stretch)
- Anything that activates inflammatory cascades may -> labour
How do progesterone levels change during pregnancy?
- Needed to sustain pregnancy (PR blockade = pregnancy loss)
- Remain high until after delivery of placenta so PR receptor must be disrupted
What causes the reduction in progesterone’s effect that allows labour to begin?
- High levels of NFkB can block PRs
- Higher proportion of PR-A, which is less effective than PR-B
