Human labour + development

Question 1

Define miscarriage

Answer 1

Delivery at <23 weeks gestation

Question 2

Define term labour

Answer 2

Delivery at 37-41 weeks gestation

Question 3

Define pre-term labour

Answer 3

Delivery at 23-37 weeks gestation

Question 4

Define labour

Answer 4

Increasing fundally dominated contractions combined with cervical ripening and effacement

Question 5

What does labour involve?

Answer 5

• Cervical ripening & effacement (increasing)
• Coordinated myometrial contractions (increasing)
• Rupture of foetal membranes
• Infant delivery then placental delivery
• Uterine contraction

Question 6

Generally how long are the 3 phases of labour and what happens in each?

Answer 6

Phase 1 - many hours - contractions, cervical changes
Phase 2 - hours - baby delivered
Phase 3 - 0.5 hours - placenta delivered

Question 7

What initiates labour during term?

Answer 7

Not entirely sure

May be high oestrogen: progesterone ratio, CRH or oxytocin

Question 8

What can initiate labour pre-term?

Answer 8

• Intrauterine infection
• Bleeding
• Multiple pregnancy
• Maternal stress

Question 9

What changes does the cervix undergo during labour?

Answer 9

Ripening & effacement:

• Change from rigid -> flexible structure
• Remodelling - loss of ECM
• Recruitment (leucocytes e.g. neutrophils)
• Inflammation (prostaglandin E2, IL-8)

Question 10

What happens to the myometrium during labour?

Answer 10

Co-ordinated myometrial contractions:

• Fundal dominance with increased power and coordination
• Mediators: increased prostaglandin F2a, increased oxytocin receptors, contraction proteins

Question 11

What happens to the foetal membranes during labour?

Answer 11

Loss of strength due to changes in amnion BM -> rupture

- Inflammation and leucocyte recruitment (exacerbated in preterm), increased MMPS (matrix metalloproteins)

Question 12

What is NFkB?

Answer 12

Pro-inflammatory transcription molecule

- Closely related to IL1b, IL6, COX2, cPLA2, IL8

Question 13

What does NFkB inititiate effects through?

Answer 13

COX2, IL8, MMPs, oxytocin receptors, PG receptors, contraction-associated proteins

Question 14

What must be constitutively expressed before any changes conducive to labour can be seen?

Answer 14

PGE2

Question 15

What factors control labour?

Answer 15

CRH & PAF -> activate other molecules and ultimately MMPs, PGE2 and upregulation of oxytocin receptors

Question 16

What produces CRH?

Answer 16

Pituitary gland AND placenta

Question 17

How do levels of CRH and CRH-binding proteins change towards the end of pregnancy?

Answer 17

CRH level: increase

CRH-binding protein: decrease

Question 18

What is the relationship between CRH and COX2 expression?

Answer 18

High CRH correlates with high COX2 expression

Question 19

What is PAF?

Answer 19

Part of lung surfactant that is produced by maturing lungs before birth

Question 20

How do levels of surfactant and therefore PAF change as the foetus nears term?

Answer 20

Surfactant: increases
PAF: increases

Question 21

What do CRH and PAF upregulate?

Answer 21

• PGE2 and COX2 expression

- IL1b levels

Question 22

What are the three theories for labour induction?

Answer 22

• 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

Question 23

How do progesterone levels change during pregnancy?

Answer 23

• Needed to sustain pregnancy (PR blockade = pregnancy loss)

- Remain high until after delivery of placenta so PR receptor must be disrupted

Question 24

What causes the reduction in progesterone’s effect that allows labour to begin?

Answer 24

• High levels of NFkB can block PRs

- Higher proportion of PR-A, which is less effective than PR-B