Abnormal Labour

Question 1

Cause of initiation of labour is relatively uncertain. However what is thought to initiate labour? (4)

Answer 1

Change in oestrogen/progesterone ratio,
Fetal adrenals & pituitary hormones may control timing,
Myometrial stretch increases excitability,
Fergusons reflex: baby’s head stretching cervix further stimulates oxytocin release repeating the cycle

Question 2

Role of oestrogen in labour

Answer 2

Promotes prostaglandin production which makes the uterus contract

Question 3

Role of oxytocin in labour

Answer 3

Oxytocin intiates and sustains contractions:
Acts on decidual tissue to promote prostaglandin release,
Also made in decidual and fetal tissues and in placenta,
Number of oxytocin receptors increases in myometrial & decidual tissues near end of preg