INDUCTION OF LABOUR

Definition: Induction is the initiation of labour by artificial means Labour should be induced for medical or obstetrical reasons. 

Induction of labor (IOL) means initiation of uterine contractions (after the period of viability) by any method (medical, surgical or combined) for the purpose of vaginal delivery. The patient and the family members are informed about the benefits, potential complications and the possibility of cesarean delivery.

  • Purpose- when the risk of continuation of pregnancy either to the mother or to the fetus is more, induction is indicated.
  1. Type 
  • Medical - using drugs alone Syntocinon & prostaglandin E2
  • Surgical-aminiotomy or membranes sweep 
  • Combined - medical & surgical. 

Indications for Induction

  1. Prolonged pregnancy (post term pregnancy) 
  2.  Pre eclampsia, eclampsia and diabetes 
  3.  Evidence of diminished fetal well being or growth 
  4. Elderly primigravida 
  5. Poor obstetric history 
  6. Spontaneous / premature rupture of membrane 
  7. Previous large baby 
  8. Rhesus iso - immunization 
  9.  Unstable lie 
  10.  Genital herpes 
  11. Previous precipitate labour 
  12.  Placenta abruptio 
  13. intrauterine death 

Contraindication 

  • Contracted pelvis and cephalopelvic disproportion
  • Malpresentation (breech, transverse or oblique lie)
  • Previous classical cesarean section or hysterotomy (scared uterus)
  • Uteroplacental factors: Unexplained vaginal bleeding, 2
  • previa, placenta previa
  • Active genital herpes infection
  • High-risk pregnancy with fetal compromise
  • Heart disease
  • Pelvic tumor
  • Elderly primigravida with obstetric or medical complications
  • Umbilical cord prolapse
  • Cervical carcinoma
  • Psychological distress 

Factors which affect induction of labour 

  • Fetal maturity and viability 
  • Favorability of cervix 

Note-Favorability of cervix is assessed by a score system called ‘’Bishop”score.It has to be done before induction. The score is scored out of 20.Score of greater or equal to 7is favorable. There are four factors considered, each accounts a score of 0-3.

Bishops Score System 

Inducibility features 0 1 2 3
Dilatation of cervix in cm Closed 1-2cm  3-4cm  5cm
Consistency of cervix Firm Medium  Soft   
Position of cervix Posterior  Medline Anterior  
Effacement of cervix % 0-30 40-50 60-70  80 
Station in cm / above -3 -2 -1,0 +1,+2

Note- Modification( 1991) replaces  effacement(%) with cervical length in cm.

Cervical length >4 2-4 1-2 <1
  • Total score=13
  • Favorable score=6-13
  • Unfevorable score =0-5

Methods 
Medical method 
1. Prostaglandin E2 

  1. Vaginal prostaglandin 
  2.  Endocervical prostaglandin 
  3. Extra amniotic prostaglandin 
  4.  Oral 

2. Intravenous oxytocin / syntocinon/ infusion 
Aim - To achieve 3 contractions per 10 minutes lasting 40-60 

  • Procedure of induction for multipara and primigravida 
Multipara Primigravida 

Start with 2.5 IU oxytocin in 1000 D/w running at 20 drops / min . If no contraction double every 20 minutes. Always stops at 80 drops (20, 40, 60, 80). 

 Start with 5 IU Oxytocin in 1000 D/w running at 20 drops per / min. If no contraction double every 20 minutes. Always stop at 80 drops 
 
If no contraction add 2.5IU 
of oxytocin and start with 60 
drops (60,80)		 If no contractions add 5 IU 
of oxytocin and start with 40 
drops 
If no contractions add 2.5IU oxytocin and start with 
40 drops (40, 60, 80) 
[Maximum7.5 units]. 		 If no contractions add 5 IU 
of oxytocin and start with 60 
drops. 
[Maximum 15 units)

In induction 

  1. delivery interval doesn’t exceed 18 hours; if not ceaserean section is indicated. 
  2.  If no labour starts in 6 hours- consult 
  3. If contractions are very strong and tetanic stop drip, sedate and consider ceaserean section. 

Observation of mother and fetus 

  • The fetal heart rate 
  • Uterine contractions 
  • Fluid balance chart 
  •  Urine test for ketoses 
  • Progress in labour 
  • Abdominal & cervical examination every 2-4 hours 
  • After delivery continue oxytocin drops for one hour to prevent PPH. 

Complications of medical induction 
 Over stimulation of the uterus causing fetal distress, precipitate labour or uterine rupture. 

  • Amniotomy (Surgical induction)

Amniotomy is artificial rupturing of amniotic bag or membranes. Rupturing these if they do not rupture spontaneously allows the fetal head to contact the cervix more 
directly and may increase the efficiency of contractions. The membranes are torn and amniotic fluid is allowed to escape. 
Complications: 

  •  Cord prolapse 
  • Placental separation 
  • Intrauterine infection if labour is not completed with is 24 hours of rupture of membrane and prophylactic antibiotic is not given. 

Contraindications: 

  1. High head 
  2.  Unripe cervix 
  3.  Malpresertaions 
  4. Intrauterine death 

COMBINED METHOD

The combined medical and surgical methods are commonly used to increase the efficacy of induction by reducing the induction-delivery interval. The oxytocin infusion is started either prior to or following rupture of the membranes depending mainly upon the state of the cervix and head brim relation.

  1. More effective than any single procedure.
  2. Shorten the induction delivery interval and thereby-
  • Minimizes the risk of infection
  • lessens the period of observation.

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