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. 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 women (the ARRIVE trial – see below in ‘Related ObG Topics’), showed no increase in perinatal morbidity and mortality rates with lower rates of cesarean delivery. The results of this trial and other more recent studies will likely further increase induction rates.

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

Cervical Ripening

• Definition: “Process of softening and effacing the cervix in preparation of labor”

Bishop Score

• Decision for cervical ripening may include the following factors
  • Bishop score range from 3 to 8 have been used in the literature
  • Parity
  • Gestational age

Cervical Ripening Agents

• Misoprostol (prostaglandin E1 [PGE1])
  • Oral
    • 25 micrograms every 2 hours or
    • 50 to 100 micrograms every 4 hours
  • Vaginal
    • 25 micrograms every 3 to 6 hours
  • Contraindication: Prior cesarean and/or uterine surgery due to risk for uterine rupture
• Dinoprostone (prostaglandin E2 [PGE2])
  • Vaginal
    • Gel: 0.5 mg every 6 hours | Maximum 3 doses (1.5 mg)
    • Insert: 10 mg vaginal insert | Maximum 12 hours

• Mechanical dilators
  • Foley catheter (30 to 80 ml): Reasonable and effective option for cervical ripening
    • No benefit to applying tension to catheter
  • Double balloon device
  • Others dilator options: Hygroscopic dilation | Osmotic dilators (Laminaria japonicum)

Note: “ACOG suggests the use of pharmacologic methods in combination with mechanical methods of cervical ripening to shorten the time from admission to delivery in appropriate candidates”

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: 4 mU (or higher) with increasing rate of 3 to 6 mU/min every 15 to 40 minutes
• Both maternal and fetal outcomes are similar with either low- or high-dose regimen
• 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 – Does not appear to result in adverse outcomes

Amniotomy

• Early amniotomy (<1 hour after foley removal)
  • Higher odds of vaginal delivery within 24 hours
  • Shorter duration of labor induction
  • No increase in cesarean or other complications
• 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

KEY POINTS:

• Prior to starting an induction of labor, contraindications should be reviewed
• Outpatient cervical ripening considered safe and effective in low-risk patients
  • Reduced time from admission to delivery
  • Evidence available for
    • Vaginal misoprostol dose of 25 micrograms (based on network meta-analysis)
    • Synthetic osmotic dilators
• 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 Clinical Practice Guideline 9: Cervical Ripening in Pregnancy

ACOG Clinical Practice Guideline 8: First and Second Stage Labor Management

Related ObG Topics:

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

ACOG Recommendations: When to Deliver Medically Complicated Pregnancies

Stillbirth: Definition, Evaluation and Management

Induction vs Expectant Management At and Beyond Term – the Cochrane Review

2020 Cochrane Review Update: How Does Membrane Sweeping Compare to Other Methods of Induction?

2021 Cochrane Review: Oral Misoprostol vs Other Labor Induction Methods

Cochrane Review Update: Safety and Effectiveness of Mechanical vs Pharmacological Methods of Labor Induction

Meta-analysis: Safety of Balloon Catheter for Induction in the Setting of Ruptured Membranes

How Safe and Effective is Early Amniotomy During Labor Induction?

How Effective is Membrane Sweeping When Inducing Labor?