Induction of Labor: Indications and Management

Bishop Score Calculator

SUMMARY:

The purpose of induction of labor is to stimulate uterine contractions before onset of spontaneous labor for vaginal delivery.  The rates of induction of labor have significantly increased during the last decades. In 1990, less than 10% of pregnancies underwent induction of labor, vs 30% by 2019.  Currently, induction of labor is one of the most frequently performed obstetric procedures. A recent RCT comparing elective induction of labor at 39 weeks gestation with expectant management in nulliparous people (the ARRIVE trial – see below in ‘Related ObG Topics’), showed no increase in perinatal morbidity and mortality rates with lower rates of cesarean delivery. These results may lead to an increase in induction rates in the near future.

Indications

Indications include but are not limited to the following

  • Maternal conditions
    • Antepartum: Abruptio placentae | Chorioamnionitis | Fetal demise | Gestational hypertension | Preeclampsia | Eclampsia | PROM | Postterm pregnancy
    • Pregestational: Diabetes mellitus | Renal disease | Chronic pulmonary disease | Chronic hypertension | Antiphospholipid syndrome
  • Fetal compromise
    • Fetal growth restriction | Isoimmunization | Oligohydramnios
  • Logistical reasons >39 weeks
    • Risk of rapid labor | Distance to hospital | Psychosocial indications

Note: See summary of guidance on timing of delivery for medical indications below in ‘Related ObG Topics’

Contraindications 

  • Similar to contraindications for vaginal delivery
    • Vasa previa or complete placenta previa
    • Transverse fetal lie
    • Umbilical cord prolapse
    • Previous classical cesarean delivery
    • Active genital herpes infection
    • Previous myomectomy entering endometrial cavity

Cervical Preparation

Bishop Score

  • A Bishop score of ≤6 is associated with low rate of successful induction with oxytocin alone, and the use of cervical ripening agents are recommended


Cervical Ripening Agents

  • Misoprostol (PGE1 analogue) given intravaginally, orally or sublingually
    • Initial dose: 25 mcg every 3 to 6 hours
    • Delay oxytocin 4 hours after last dose
    • Available evidence supports safety and efficacy
    • Higher rates of tachysystole
      • When compared to PGE2
      • With dosing ≥50 mcg
    • Contraindications: Prior cesarean and/or uterine surgery due to risk for uterine rupture
  • Dinoprostone (PGE2 preparations) given vaginally via gel or insert
    • 0.5 mg in 2.5 ml syringe gel or 10 mg vaginal insert
    • Second dose after 6 to 12 h (maximum dose of 1.5 mg in 24 hours)
    • Delay oxytocin 6 to 12 hours after last application of gel or 30 to 60 min after insert

Note: After prostaglandin use (misoprostol or dinoprostone), patient should remain recumbent for at least 30 minutes | Fetal heart tracing should be monitored continuously for 30 minutes to 2 hours | FHR monitoring should be continued if regular uterine contractions are persistent

  • Mechanical dilators
    • Foley catheter ( 30 to 80 ml): Reasonable and effective option for cervical ripening
    • Double balloon device
    • Others dilator options: Hygroscopic dilation | Osmotic dilators (Laminaria japonicum) | Extra amniotic saline infusion

Methods of Induction 

Oxytocin

  • Pitocin is synthetic formulation for oxytocin, with both low-dose and high-dose regimens
    • Low-dose regimen: 0.5 to 2 mU with increasing rate of 1 to 2 mU/min every 15 to 40 minutes
    • High-dose regimen: 6 mU with increasing rate of 3 to 6 mU/min every 15 to 40 minutes
  • High-dose regimen:
    • Shorter labor | Less chorioamnionitis | Less cesarean
    • More tachysystole with FHR changes
  • Myometrium becomes more sensitive to oxytocin increases with advancing gestation
  • Management of tachysystole with FHR changes
    • Decrease/discontinue oxytocin
    • Corrective measures: Turn patient on side | Oxygen | Fluids | Terbutaline

Membrane Stripping

  • Mechanical technique
    • Insertion of one or two fingers into the cervix | Continuous circular sweeping motion detaches the inferior pole of the membranes from the lower uterine segment
  • Reduces rates of formal induction (2.3% vs 3.1%) and increases rates of spontaneous labor (72% vs 60%)
  • Positive GBS – insufficient data for recommendation

Amniotomy

  • Better when cervix is favorable
  • In combination with oxytocin: Reduces interval from induction to delivery by approximately 5 hours
  • Risks: Cord prolapse | Chorioamnionitis
  • Avoid, if possible: HIV, hepatitis B or hepatitis C
  • Positive GBS: No data to suggest increased risk for neonatal disease when appropriate intrapartum antibiotic prophylaxis is given

Nipple Stimulation

  • Increase likelihood of labor when cervix is favorable
  • Only studied in low-risk populations
  • In meta-analysis
    • Decrease in women not in labor after 72 hours
    • Decrease in PPH
    • No impact on meconium-stained amniotic fluid or cesarean delivery
    • Due to association with an increased trend toward association with perinatal death “this practice is not recommended in an unmonitored setting”

Specific Clinical Scenarios 

Ruptured Membranes

  • Induction with oxytocin is associated with decreased
    • Interval between PROM and delivery
    • Frequency of chorioamnionitis
    • Postpartum febrile morbidity
  • Prostaglandins appear safe and effective

Intrauterine Fetal Demise

ACOG 2020

  • <28 weeks
    • Misoprostol 400 to 600 mcg vaginally every 4 to 6 hours
  • >28 weeks
    • Standard obstetric protocol for labor induction
  • Prior uterine scar
    • <28 weeks: Lower doses of Misoprostol (200 mcg) may be preferred
    • >28 weeks: Foley for cervical ripening
  • Prior classical incision
    • Limited data to guide clinical practice

SFP 2013

  • <28 weeks
    • Misoprostol-only: 100 to 200 mcg vaginally every 4 hours
    • Misprostol-mifepristone regimen: Mifepristone 200 mcg or 600 mcg, followed by misoprotol 36 to 48 hours later | Misoprostol 200 mcg or 400 mcg every 4 hours
    • Addition of mifepristone may shorten the time to expulsion
  • Prior uterine scar
    • Consider using 200 mcg or less per dose of misoprostol
    • Insufficient data to advise change in dosing interval

KEY POINTS:

  • Prior to starting an induction of labor, contraindications should be reviewed
  • Cervical ripening is recommended with a Bishop score of ≤6
  • Predictors of induction success
    • Lower BMI | Greater dilation | Higher parity | Term gestational age
  • Pharmacologic and non-pharmacologic methods can be used for induction based on the patient’s characteristics
  • Misoprostol regimens are recommended for intrauterine fetal demise including TOLAC
  • There is no strong consensus to define failed induction
    • At least 12 to 18 hours of latent labor with oxytocin and AROM should be allowed before diagnosing failed induction

Learn More – Primary Sources:

ACOG Practice Bulletin 107: Induction of Labor

Society of Family Planning: Interruption of nonviable pregnancies of 24–28 weeks’ gestation using medical methods

The ARRIVE Trial and Professional Guidance: Elective 39 Week Induction to Reduce the Risk of Cesarean Section

SUMMARY:  

The ARRIVE study (A Randomized Trial of Induction Versus Expectant Management), authored by Grobman et al. (NEJM, 2018), was undertaken to determine if elective induction of labor (IOL) of low-risk nulliparous women at 39 weeks reduces adverse perinatal and neonatal morbidity compared to expectant management. SMFM released a statement, endorsed by ACOG, addressing the ARRIVE findings.

SMFM Recommendations

It is reasonable to offer elective IOL to low-risk, nulliparous women at or beyond 39 weeks and 0 days of gestation. We recommend that providers who choose this approach ensure that women meet eligibility criteria of the ARRIVE trial.

We recommend against offering elective IOL to women under circumstances that are inconsistent with the ARRIVE study protocol unless performed as part of research or quality improvement.

We recommend that further research be conducted to measure the impact of this practice in settings other than a clinical trial.

Study Highlights 

Methods 

    • Multicenter, randomized, controlled, parallel-group, unmasked trial
        • Low-risk nulliparous women between 34w0d-38w6d
        • Live singleton, vertex fetus
        • No contraindications to vaginal delivery
      • No planned cesarean deliver
    • Low-risk
      • No maternal or fetal condition that would be an indication for delivery <40w5d
    • Randomization
        • Induction group: IOL at 39w0d-39w4d
      • Expectant group: No elective delivery <40w5d and begin delivery no later than 42w2d
    • Primary outcome
      • Composite of perinatal death or severe neonatal complications
  • Secondary outcomes
    • Multiple neonatal and maternal outcomes including mode of delivery

Results 

    • 3,062 women labor induction group | 3,044 expectant management group
    • Primary outcome not statistically different
      • 4.3% of neonates in induction group vs 5.4% in the expectant group
      • Relative risk (RR) 0.80; 95% CI, 0.64-1.00 (P=0.049)
        • To account for an interim analysis, a two-tailed P value of <0.046 was used for statistical significance threshold
    • Cesarean delivery was less frequent in the induced labor group (19%) vs the expectant management group (22%) 
      • RR 0.84; 95% CI 0.76-0.93
    • Preeclampsia and gestational hypertension occurred in 9.1% of the induced group vs 14.1% of the expectant management group 
      • RR 0.64; 95% CI 0.56-0.74
  • Among newborns, 3% in the induced group needed respiratory support vs 4.2% in the expectant management group
    • RR 0.71; 95% CI 0.55-0.93

Conclusions 

  • There was no difference between groups with respect to composite adverse perinatal outcome, but there was reduced frequency of cesarean section in the induction group
  • There was increased incidence of maternal hypertension/preeclampsia and newborn respiratory support in the expectant management group
  • The authors state

Our data suggest that 1 cesarean delivery may be avoided for every 28 deliveries among low-risk nulliparous women who plan to undergo elective induction of labor at 39 weeks.

KEY POINTS:  

Induction Protocol Highlights

  • Patients had a cervical exam between 72 hours prior to randomization and 24 hours after randomization
  • IOL protocol
    • Induction using oxytocin
    • Unfavorable cervix (modified Bishop score <5) underwent cervical ripening
      • method left to patient’s physician’s discretion
      • with or followed by oxytocin stimulation
  • ‘Failed’ Labor in latent phase
    • At least 12 hours after completion of cervical ripening, rupture of membranes, and use of a uterine stimulant
    • Cesarean decision left to patient’s physician’s discretion
  • Additional SMFM recommendations
    • Shared decision making is ‘critical’
    • All women in this study had ultrasound dating, early in pregnancy
      • Certain LMP: <21 weeks
      • Uncertain LMP: First trimester ultrasound
  • ACOG has also released a Practice Advisory related to ARRIVE (see ‘Learn More-Primary Sources’ below) that also highlights the importance of shared decision making as well as taking in to account “resources available (including personnel), and the setting in which the intervention will be implemented”

Learn More – Primary Sources:

Labor Induction versus Expectant Management in Low-Risk Nulliparous Women

SMFM Statement: Elective induction of labor in low-risk nulliparous women at term: The ARRIVE trial

ACOG Practice Advisory: Clinical guidance for integration of the findings of The ARRIVE Trial: Labor Induction versus Expectant Management in Low-Risk Nulliparous Women