Induction of labour

• Induction of labour (IOL) refers to the use of medications to stimulate the onset of labour.
• Induction of labour can be used where patients go over the due date. IOL is offered between 41 and 42 weeks gestation.
• Induction of labour is also offered in situations where it is beneficial to start labour early, such as:

  • Prelabour rupture of membranes
  • Fetal growth restriction
  • Pre-eclampsia
  • Obstetric cholestasis
  • Existing diabetes
  • Intrauterine fetal death
• Bishop score:

  • Scoring system used to determine whether to induce labour
  • 5 things are assessed and given a score - max score 13
  • Includes cervical position, dilation and effacement
  • A score of 8 or more predicts a successful induction of labour
  • A score below 8 suggests cervical ripening may be required e.g. vaginal misoprostol
• Options for IOL:

  • Membrane sweep - outpatient
  • Vaginal prostaglandin E2 - inserted into the vagina and stimulates the cervix and uterus - usually done in hospital setting
  • Cervical ripening balloon - silicone balloon inserted into cervix and gently inflated to dilate cervix. Usually used if prostaglandins failed
  • Artificial rupture of membranes with an oxytocin infusion
• Most women will give birth within 24 hours of the start of induction of labour.

  The options when there is slow or no progress are:

  • Further vaginal prostaglandins
  • Artificial rupture of membranes and oxytocin infusion
  • Cervical ripening balloon (CRB)
  • Elective caesarean section
• Uterine hyperstimulation:

  • Main complication of induction of labour with vaginal prostaglandins
  • Contraction of the uterus is prolonged and frequent, causing fetal distress and compromise
  • Individual uterine contractions lasting more than 2 minutes
  • Or more than 5 contractions every 10 minutes
• Uterine hyperstimulation can lead to:

  • Fetal compromise, with hypoxia and acidosis
  • Emergency caesarean section
  • Uterine rupture
• Management of uterine hyperstimulation involves:

  • Removing the vaginal prostaglandins, or stopping the oxytocin infusion
  • Tocolysis with terbutaline - beta-2 adrenergic receptor agonist - relaxes myometrium