INDUCTION OF LABOUR (I.O.L.)

1. INDUCTIONOF LABOUR (I.O.L.) Dr. Ahmed Al Harbi Obstetrics/Gynecology Consultant

2. Definition: The planned initiation of labour prior to its spontaneous onset. Between 15 % and 25% of all pregnancies in the UK end as in IOL.

3. It should only be performed if there is a reasonable chance of success and if the risks of the process to the mother and/or fetus are acceptable. If either of these is not the case, a planned Caesarean section should be performed instead.

4. The most common reason for IOL is ‘post dates’ or ‘post-maturity’. There is evidence that prolonged pregnancies extending beyond 42 weeks’ gestation are associated with a higher risk of stillbirth, fetal compromise in labour, meconium aspiration and mechanical problems at delivery.

5. Prolonged prelabour rupture of membranes (PPROM), the longer this situations left to continue, the greater risk of ascending infection (chorioamnionitis)

6. Common Indications for IOL: ‘Post Dates’ (i.e. 12 days or more beyond EDD) Fetal growth restriction. Other evidence of placental insufficiancy, e.g. oligohydramnios Pre-eclampsia Other maternal hypertensive disorders.

7. Deteriorating maternal illnesses Prolonged prelabour rupture of membranes Unexplained antepartumhaemorrhage Diabetes Mellitus Twin pregnancy continuing beyond 38 weeks Rhesus iso-immunization ‘Social’ reasons

8. The Bishop Score Bishop produced a scoring system to quantify how far this process had progressed prior to the IOL. High scores (a ‘favourable’ cervix) are associated with an easier, shorter induction that is less likely to fail. Low scores (a ‘unfavourable’ cervix) point to a longer IOL that is more likely to fail and result in Caesarean section.

10. Methods: ARM was traditionally performed Synthetic Oxytocin became available in the 1950’s and was used as an intravenous adjunct after rapture of membranes. * Prostaglandin became available in the 1960’s. Various routes and various preparations have been used, but the most common formulation in current use is inserted vaginally into the posterior fornix as tablet or gel.

11. Complications of IOL: CTG should be performed at the start of every induction of labour and is normally continued throughout the process. Many indications for IOL will be associated with a higher risk of fetal compromise in labour, as is the use of prostaglandins and oxytocin.

12. IOL may fail and result in Caesarean section. An induction is said to have failed if an ARM is still impossible after the maximum number of doses of prostaglandin have been given, or if the cervix remains uneffaced and <3 cm dilated after an ARM has been performed and syntocinon has been running for 6-8 hours.

13. Hyperstimulation of the uterus (from prostaglandin administration or use of Syntocinon) may result in fetal asphyxia and the need for Caesarean section. IOL in the presence of a uterine scar may lead to uterine rupture. ARM performed when the presenting part is still high risks cord prolapse.

14. IOL is associated with a longer duration of labour, greater use of epidurals and more assisted vaginal deliveries. Long labours augmented with Syntocinon predipose to postpartum haemorrhage due to uterine atony after delivery of the placenta.

15.  THE END 