Low dose oral misoprostol for induction of labour

Prostaglandins have been used since the 1960s for induction of labour

• have been shown to promote cervical ripening, the process where the cervix softens, effaces (shortens) and dilates as it prepares for labour
• use has been shown to reduce caesarean sections in induction of labour when compared to using oxytocin alone
• misoprostol modifies cervical collagen, resulting in cervical ripening, and also stimulates uterine activity
  • possible routes of administration:
    • oral,
    • vaginal,
    • rectal,
    • buccal (dissolved in the cheek) and
    • sublingual (dissolved under the tongue)
    • most common routes of administration for labour induction are oral and vaginal
      • oral misoprostol is absorbed quickly with a faster onset of action;
      • vaginal misoprostol is absorbed more slowly, though its action is more prolonged
        • vaginal misoprostol may also have locally mediated effects on the uterus, independent of serum level (1)
• low-dose oral misoprostol is probably associated with fewer caesarean sections (and therefore more vaginal births) than vaginal dinoprostone, and lower rates of hyperstimulation with foetal heart rate changes. However, time to birth may be increased, as seen by a reduced number of vaginal births within 24 hours
  
  
• compared to transcervical Foley catheter, low-dose oral misoprostol is associated with fewer caesarean sections, but equivalent rates of hyperstimulation (2)
  
  
• low-dose misoprostol given orally rather than vaginally is probably associated with similar rates of vaginal birth, although rates may be lower within the first 24 hours (2)
  • is likely less hyperstimulation with foetal heart changes, and fewer caesarean sections performed due to foetal distress with low-dose oral misoprostol
    
    
• available evidence suggests that low-dose oral misoprostol probably has many benefits over other methods for labour induction (2)
  • review supports the use of low-dose oral misoprostol for induction of labour, and demonstrates the lower risks of hyperstimulation than when misoprostol is given vaginally

NICE note that (3):

• discuss with women the risks and benefits of different methods to induce labour. Include that:
  • both dinoprostone and misoprostol can cause hyperstimulation
    • hyperstimulation is overactivity of the uterus as a result of induction of labour
      • is variously defined as uterine tachysystole (more than 5 contractions per 10 minutes for at least 20 minutes) and uterine hypersystole/hypertonicity (a contraction lasting at least 2 minutes)
      • may or may not be associated with changes in the fetal heart rate pattern (persistent decelerations, tachycardia or increased/decreased short term variability)
  • when using pharmacological methods of induction, uterine activity and fetal condition must be monitored regularly
  • if hyperstimulation does occur, the induction treatment will be stopped by giving no further medication, or by removal of vaginally administered products when possible
  • there are differences in the ease with which different vaginal products can be removed (for example, dinoprostone controlled-release vaginal delivery systems can be more easily removed than gel or vaginal tablets)
  • hyperstimulation can be treated with tocolysis, but hyperstimulation caused by misoprostol may be more difficult to reverse
  • mechanical methods are less likely to cause hyperstimulation than pharmacological methods
• for women with a Bishop score of 6 or less, offer induction of labour with dinoprostone as vaginal tablet, vaginal gel or controlled-release vaginal delivery system or with low dose (25 microgram) oral misoprostol tablets
• for women with a Bishop score of 6 or less, consider a mechanical method to induce labour (for example, a balloon catheter or osmotic cervical dilator) if:
  • pharmacological methods are not suitable (for example, in women with a higher risk of, or from, hyperstimulation, or those who have had a previous caesarean birth), or
  • the woman chooses to use a mechanical method
• for women with a Bishop score of more than 6, offer induction of labour with amniotomy and an intravenous oxytocin infusion
  • advise women that they can have an amniotomy and can choose whether or not to have an oxytocin infusion, or can delay starting this, but that this may mean labour takes longer and there may be an increased risk of neonatal infection

Reference

• Hofmeyr GJ et al. Vaginal misoprostol for cervical ripening and induction of labour. Cochrane Database of Systematic Reviews 2010, Issue 10. Art. No: CD000941
• Kerr RS, Kumar N, Williams MJ, Cuthbert A, Aflaifel N, Haas DM, Weeks AD. Low-dose oral misoprostol for induction of labour. Cochrane Database of Systematic Reviews 2021, Issue 6. Art. No.: CD014484. DOI: 10.1002/14651858.CD014484
• NICE (November 2021). Induction of labour.