Induction of Labor

Objectives Definitions Indications and contraindications Pregnancy dating Comparison of methods Management considerations

Induction initiation of uterine activity and cervical change with fetal descent by pharmacological or other means in a woman who is not in labor.

Cervical Ripening promotion of cervical change by pharmacological or other means not primarily intended to induce labor but to increase the success of subsequent induction

Contraindications to Induction Any contraindication to labor

Indications for Induction when continuation of the pregnancy is a greater risk to the mother or fetus than the risk of induction and delivery must be convincing, compelling, fully discussed and documented

Indications - Emergent severe gestational hypertension suspected acute fetal compromise severe IUGR significant maternal disease not responding to treatment significant APH chorioamnionitis

Indications - Urgent PROM at term or near term IUGR without evidence of acute compromise poorly controlled diabetes mellitus isoimmune disease at term or near term

Indications - Non-Urgent 'post-term' pregnancy well controlled diabetes mellitus intrauterine death in a prior pregnancy intrauterine fetal demise logistic problems (rapid labours, distance to hospital)

Indications - NOT elective induction induction, in the absence of maternal or fetal indication, should not be undertaken

Risks of Induction failure to achieve labour uterine hyperstimulation with fetal compromise uterine hyperstimulation with uterine rupture increase risk of C/S

Labour Induction Methods Likelihood of Successful Vaginal Delivery MOST MOST favourable multiparous previous vaginal cervix delivery unfavourable nulliparous cervix previous C/S LEAST LEAST

If attempted induction does not achieve labor reevaluate the indication and method of induction

Methods of induction include mechanical and pharmacological means. The best choice depends on the cervical score (A cervix is unfavorable if the Bishop score is < 6)

Bishop Scoring System Factor 1 2 3 Dilatation (cm) 1 - 2 3 - 4 > 5 Score Factor 1 2 3 Dilatation (cm) 1 - 2 3 - 4 > 5 Effacement (%) 0 - 30 40 - 50 60 - 70 > 80 Consistency Firm Medium Soft Position Posterior Mid Anterior Sp -3 or Sp +1 or Station Sp -2 Sp -1 or 0 above lower

Effect of Cervical Status on C/S Rate 50 Nulliparous Parous 40 34 30 23 20 Cesarean Section (%) 20 13 12 6 10 0-3 >3 Spontaneous Labour Cervical dilatation at induction Xenakis Obstet Gynecol (1997) 90: 235

Labour Induction - Unfavourable Cervix Stripping of membranes Cervical ripening followed by oxytocin laminaria / artificial tents Foley catheter prostaglandins Prostaglandins (intracervical or vaginal) Amniotomy or oxytocin

Mechanical Methods catheters and tents cause cervical softening and effacement this may facilitate an early amniotomy these methods are effective by producing local prostaglandin along with direct dilatation less hypertonus and FH rate abnormalities than with pharmacologic agent

Prostaglandin Preparations Vaginal preparations are: easier to administer easier to remove less likely to be placed extra-amniotically less likely to cause patient discomfort

Prostaglandin E2 myometrial contraction cervix causes collagen breakdown and proteoglycan deposition vasodilator bronchodilator GI motility and secretory effects

Prostaglandin E2 - Route and Dose intracervical (Prepidil ) prostaglandin E2 0.5 mg into cervical canal vaginal (Prostin E2 vaginal gel ) prostaglandin E2 1 or 2 mg into posterior fornix vaginal (Cervidil vaginal insert) prostaglandin E2 10 mg into posterior fornix any formulation may be used for cervical ripening

Guidelines for PGE2 Use insertion in hospital by experienced caregiver monitor appropriately for FHR and uterine activity if labour develops manage as appropriate if no labour, reassess, repeat as necessary or choose an alternative induction method

Prostaglandin E2 - Advantages improved patient acceptance lower operative delivery rate less need for oxytocin induction may be used in PROM cost considerations

Prostaglandin E2 - Disadvantages adverse reactions hyperstimulation CVS events nausea, vomiting, diarrhea gel preparations are difficult to remove cost considerations

Precautions with Prostaglandins avoid placing PG’s adjacent to myometrium use cautiously in patients with previous C/S do not repeat more frequently than every 6 hours wait 6 hours prior to oxytocin infusion following gels may be started 30 minutes after Cervidil removal do not use for augmentation

Labour Induction - Favourable Cervix Stripping of membranes Amniotomy Oxytocin Vaginal prostaglandins

Amniotomy creates commitment to delivery effective with favourable cervix often used in conjunction with oxytocin caution in cases of high presenting part ( risk of cord prolapse)

Oxytocin Effects myometrial contraction cervix - no direct effect vasoactive hypotension possible with bolus IV administration antidiuretic activity water intoxication possible with high dose oxytocin

Oxytocin Guidelines cervix should be favourable experienced caregivers and access to caesarean delivery auscultation or EFM depending on indication administration intravenous concentrations vary but avoid large free water load

Uterine Hypertonus discontinue oxytocin if in use intravenous bolus prepare for emergency delivery consider tocolytic agents ritodrine at 250 - 500 mg/min IV until desired effect nitroglycerin 50 mg IV push to maximum of 200 mg nitroglycerin spray sublingual

Post partum consideration: if oxytocin was used in labor, PPH may occur for all induced patients , give oxytocin bolus post partum ( oxytocin 10 units I.M. 20 units 1L at 100 cc/hr for 2 hours or more

Conclusions reasons for induction must be compelling, convincing and documented risk and benefits must be discussed with patient patient preference must be considered ripen the cervix as much as possible match the method with the urgency and cervical status do not use oxytocin if cervix unfavourable don't overestimate your ability to succeed

happy baby + happy mom + vaginal delivery Goal of Induction avert anticipated adverse outcome associated with continuation of pregnancy to effect uterine activity sufficient for cervical change and fetal descent without causing uterine hyperstimulation or fetal compromise to allow as natural a birthing experience as safely possible and maximize maternal satisfaction happy baby + happy mom + vaginal delivery