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Toronto Notes 2019
Induction of Labour
Obstetrics OB37
Table 21. Bishop Score
Cervical Characteristic 0 1
Position Posterior Mid Consistency Firm Medium Effacement (%) 0-30 40-50 Dilatation (cm) 0 1-2 Station of Fetal Head -3 -2
Indications
2 3
Anterior –
Soft
60-70
3-4 ≥5
-1, 0
+1, +2, +3
– ≥80
Induction vs. Augmentation
Induction is the artificial initiation of labour Augmentation promotes contractions when spontaneous contractions are inadequate
Consider the Following Before Induction
• Indication for induction • Contraindications
• GA
• Cervical favourability • Fetal presentation
• Potential for CPD
• Fetal well-being/FHR • Membrane status
• post-datespregnancy(generally>41wk)=mostcommonreasonforinduction • maternalfactors
■ DM = second most common reason for induction
■ gestational HTN ≥37 wk
■ preeclampsia
■ other maternal medical problems, e.g. renal or lung disease, chronic hypertension, cholestasis ■ maternal age over 40
• maternal-fetalfactors
■ isoimmunization, PROM, chorioamnionitis
• fetalfactors
■ suspected fetal jeopardy as evidenced by biochemical or biophysical indications
■ macrosomia, fetal demise, IUGR, oligo/polyhydraminos, anomalies requiring surgical intervention,
twins
■ previous stillbirth, low PAPP-A
Risks
• failuretoachievelabourand/orvaginalbirth
• uterinehyperstimulationwithfetalcompromiseoruterinerupture • maternalsideeffectstomedications
• uterineatonyandPPH
Contraindications
• maternal
■ prior classical or inverted T-incision C/S or uterine surgery (e.g. myomectomy) ■ unstable maternal condition
■ active maternal genital herpes
■ invasive cervical carcinoma
■ pelvic structure deformities
• maternal-fetal
■ placenta previa or vasa previa ■ cord presentation
• fetal
■ fetal distress, malpresentation/abnormal lie, preterm fetus without lung maturity
Induction Methods
CERVICAL RIPENING
Definition
• useofmedicationsorothermeanstosoften,efface,anddilatethecervix;increaseslikelihoodof successful induction
• ripeningofanunfavourablecervix(Bishopscore<6)iswarrantedpriortoinductionoflabour
Methods
• intravaginalprostaglandinPGE2gel(Prostin®gel):longandclosedcervix
■ recommended dosing interval of prostaglandin gel is every 6-12 h up to 3 doses
• intravaginalPGE2(Cervidil®):longandclosedcervix,mayuseifROM ■ continuous release, can be removed if needed
■ controlled release PGE2
• intracervical PGE2 (Prepidil®)
• intravaginal PGE1 Misoprostol (Cytotec®): long and closed cervix
■ inexpensive, stored at room temperature
■ more effective than PGE2 for achieving vaginal delivery and less epidural use • Foleycatheterplacementtomechanicallydilatethecervix
Evidence for Cervical Ripening Methods (SOGC Guidelines)
• Meta-analysis of five trials has concluded
that the use of oxytocin to ripen the cervix
is not effective
• Since the best dose and route of
misoprostol for labour induction with a
live fetus are not known and there are concerns regarding hyperstimulation, the use of misoprostol for induction of labour should be within clinical trials only (Level Ib evidence) or in cases of intrauterine fetal death to initiate labour
Intravaginal PGE2 (Cervidil®) Compared to Intravaginal Prostaglandin Gel
4 RCTs have compared the two with varying results, depending on the dosing regime of gel used.
Theoretical advantages of Cervidil®:
• Slow, continuous release
• Only one dose required
• Ability to use oxytocin 30 min after removal
vs. 6 hours for gel
• Ability to remove insert if required (i.e.
excessive uterine activity)