Labour + Adaptation to Birth

Question 1

Role of progesterone in labour

Answer 1

Keeps the uterus settled.
Prevents the formation of gap junctions
Hinders the contractibility of myocytes

Question 2

Role of oestrogen in labour

Answer 2

Makes the uterus contract
Promotes prostaglandin production

Question 3

Role of oxytocin in labour

Answer 3

Initiates and sustains contractions
Acts on decidual tissue to promote prostaglandin release
Oxytocin is synthesized directly in decidual and extraembryonic foetal tissues and in the placenta

Question 4

What happens in cervical ripening?

Answer 4

Decrease in collagen fibre alignment
Decrease in collagen fibre strength
Decrease in tensile strength of the cervical matrix
Increase in cervical decorin (dermatan sulphate proteoglycan 2)
Excess of cervical decorin near-term is capable if initiating a decorin-collagen interaction that leads to collagen fibril disruption and decreased cervical tensile strength

Question 5

What are Braxton-Hicks contractions?

Answer 5

False labour

Question 6

Features of true labour contractions

Answer 6

Evenly spaced - the time between them gets shorter and shorter (three minutes apart, then two minutes, then one)
The length of time contraction lasts also increases 10secs - 45secs
More intense and painful over time
Contractions tighten the top part of your uterus pushing the baby downward into the birth canal in preparation for delivery.
This also promotes thinning of the cervix

Question 7

Causes of PPH

Answer 7

4 Ts:
Tone
Trauma
Tissue (spare tissue in uterus)
Thrombin

Question 8

1st line in PPH when 4 Ts are not the cause

Answer 8

Intrauterine balloon
B lynch sutures - braces to keep uterus contracted

• may require hysterectomy

Question 9

Separation of placenta before birth =

Answer 9

Abruption

Question 10

How much neonatal weight loss is considered normal?

Answer 10

10%

Birth weight is regained in approx. 10-14 days

Question 11

Primary method of neonatal heat production after 12 hours?

Answer 11

Non-shivering thermogenesis
- Heat produced by breakdown of stored brown adipose tissue in response to catecholamines
- Not efficient in the first 12 hours of life

Question 12

Lower limit of normal glucose in adults is 2.6mmol/L. What if a newborn is <2mmol/L?

Answer 12

This is normal. Neonates can use ketones and lactate as brain fuel.

Question 13

Circulatory transition for neonates (6 steps)

Answer 13

1. Pulmonary vascular resistance drops (baby breathes)
2. Systemic vascular resistance rises (cord clamped / cut)
3. Oxygen tension rises
4. Circulating prostaglandins drop
5. Duct constricts
6. Foramen ovale closes

Question 14

What makes the neonate’s ductus arteriosus constrict?

Answer 14

Increased pO2
Decreased flow
Decreased prostaglandins