labour

Question 1

factors involved in initiation of labour (3)

Answer 1

1. ↓progesterone:↑oestrogen
   Functional progesterone withdrawal; multiple theories
   a.↑PR-A:PR-B (PR-A antagonistic)
   b. NFkB → ↓PR

Stretch of myometrium → upregulation of contraction associated proteins: connexins, COX-2, OTR

2. Oxytocin → NFkB → COX-2, cytokines
   a. ILβ → drives further COX-2 and PGE2 production (augment response)
   b. ILβ → cervical ripening, fetal membrane changes
   c. IL-8 → inflammatory cell influx into cervix and myometrium
3. COX-2 → prostaglandin (PGE2) → ↓collagen, ↑leukocyte migration, cervical ripening, uterine contractions
4. Fetal cortisol
   a. CRH levels rise early in some cases of PTL
   b. CRH shown to increase COX-2 and PG synthesis

Question 2

phases of parturition

Answer 2

Phase 0: progesterone → myometrial repression: firm & relaxed to accommodate growing fetus
Phase 1: myometrial activation, membrane activation (preparing for labour)
Phase 2: uterine contractions, cervical dilatation
Resembles inflammatory reaction: ↑cytokines (IL-1β, IL-6, IL-8), ↑prostaglandins, influx of neutrophils into uterus
Phase 3: uterine involution

Question 3

management of preterm labour (6)

Answer 3

1. Cervical cerclage: suture to hold cervix closed
2. Tocolytics: oxytocin receptor antagonists and CCBs e.g. nifedipine
   a. Inhibit uterine contractions
   b. Inhibit membrane activation
   c. Inhibit cervical remodelling
3. Corticosteroids: accelerate lung maturity
4. NSAIDs: inhibition of COX-1/2
5. Progesterone: inhibit production of pro-inflammatory cytokines and prostaglandins within uterus and inhibits myometrial contractility
6. Antibacterial therapy

Question 4

risk factors/causes of preterm labour (7)

Answer 4

1. Previous preterm delivery
2. Infection: contributes to 25% of PTB
3. Uterine over-distension: multiple pregnancy, polyhydramnios
   Stretch → ↑upregulation of contraction associated proteins: COX-2, OTR (oxytocin receptor)
4. Cervical weakness
5. Uterine abnormalities
6. Fetal and maternal stress
7. Iatrogenic induction of labour e.g. in pre-eclampsia, haemolytic disease of the newborn

Question 5

mechanism of infection causing preterm labour

SAQ 2016

Answer 5

1. Pathogens w no cell wall → TLR2/TLR6
2. Gram +ve bacteria → TLR2/TLR1
3. Gram -ve bacteria → TLR4
   All activate NFkB → cervical ripening, fetal membrane remodelling, uterine contractions

Question 6

management of abnormal labour (4)

Answer 6

1. Augmentation: oxytocin, if problem w power
2. ARM: artificial rupture of membranes
3. Operative vaginal delivery
   By ventouse (vacuum-assisted delivery) or forceps
   Risks: postpartum haemorrhage, fetal intracranial haemorrhage, facial/brachial palsy
4. Cesarean delivery