Labor Induction

Aka: Labor Induction, Labor Augmentation, Medical Induction of Labor, Oxytocin Induction of Labor, Oxytocin Induction, Pitocin Induction, Oxytocin Augmentation, Pitocin Augmentation

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II. Epidemiology

  1. Performed in one quarter of pregnancies in U.S.

III. Documentation

  1. Indication for Labor Induction
  2. Estimated fetal weight
  3. Fetal Position by Ultrasound
  4. Lung maturity for elective induction before 39 weeks
  5. Normal Fetal Assessment

IV. Indications: Labor Induction

  1. Rupture of Membranes at term
    1. See Premature Rupture of Membranes for preterm protocol
  2. Gestation >39 weeks AND Bishop Score >= 5
    1. See Cervical Ripening for Bishop Score <5
    2. Outcomes
      1. Labor Induction outcomes at 41 weeks are similar to those at 42 weeks
      2. Post-term pregnancies beyond 42 weeks are associated with increased neonatal morbidity
      3. (2014) Obstet Gynecol 124(2 pt 1): 390-6 +PMID: 25050770 [PubMed]
    3. Induction after 39 weeks (compared with 41 weeks) in Nulliparous women had better outcomes
      1. Fewer C-Sections (NNT 28)
      2. Decreased Pregnancy Induced Hypertension (NNT 17)
      3. Less need for newborn respiratory support in first 3 days of life (NNT 83)
      4. Grobman (2018) N Engl J Med 379(6): 513-23 +PMID: 30089070 [PubMed]
  3. Risks of contuining pregnancy exceed the risks of induction
    1. Poorly controlled maternal Hypertension (36 to 38 weeks)
    2. Pregnancy Induced Hypertension (>37 weeks)
    3. Severe Preeclampsia (>34 weeks)
    4. Gestational Diabetes (39 to 40 weeks, earlier if poorly controlled)
    5. Cholestasis of Pregnancy (36 to 39 weeks)
    6. Placenta Previa (36 to 38 weeks)
    7. Placenta accreta (34 to 36 weeks)
    8. Vasa Previa (34 to 37 weeks)
    9. Single fetus IUGR (38 to 39 weeks, or 34 to 38 weeks if complicated)
    10. Twin GestationIUGR (36 to 38 weeks, or 32 to 35 weeks if monochorionic or other complication)
    11. Twin Gestation dichorionic diamniotic (38 to 39 weeks)
    12. Twin Gestation monochorionic (34 to 38 weeks if diamniotic, or 32 to 34 weeks if monoamniotic)
    13. Oligohydramnios (36 to 38 weeks)
    14. Polyhydramnios (39 to 41 weeks)
    15. Alloimmunization (37 to 39 weeks)
  4. References
    1. (2021) Obstet Gynecol 138(1): e35-9 +PMID: 34259491 [PubMed]

V. Indications: Labor Augmentation

  1. Failure to Progress (Labor Dystocia)

VI. Approach

  1. Cervical Ripening
    1. Perform prior to induction if Cervix unfavorable (Bishop Score <5, ultrasound Cervical Length >28 mm)
  2. Consider Amniotomy

VII. Preparation: Oxytocin in Normal Saline Infusion

  1. Oxytocin 10 units in 1000 ml Normal Saline
    1. Starting rate of 6-12 ml/hour delivers 1-2 mU/minute
    2. Increasing rate 6 ml/hour delivers another 1 mU/min
  2. Oxytocin 20 units in 1000 ml Normal Saline
    1. Starting rate of 3-6 ml/hour delivers 1-2 mU/minute
    2. Increasing rate 3 ml/hour delivers another 1 mU/min

VIII. Protocol: Low Dose

  1. See Monitoring below
  2. Start: 0.5 to 2 mIU/minute
  3. Increase: 1-2 mU/minute every 15-40 minutes
    1. Base Pitocin rate changes on contractions
    2. After 8 mIU/minute, may then increase by 2 mIU/minute
  4. Maximum: 40 mIU/minute

IX. Protocol: High Dose

  1. Low dose protocol is preferred in all patients (see efficacy below)
  2. Use only in Nulliparous patients only
  3. See Monitoring below
  4. Start: 6 mIU/minute
  5. Increase: 3-6 mIU/minute every 15-40 minutes
  6. Maximum: 40-42 mIU/minute
  7. As of 2019, evidence is against the use of high dose Oxytocin (See efficacy below)

X. Monitoring

  1. Maternal Vital Signs
  2. Continuous Electronic Fetal Monitoring (CEFM)
  3. Intrauterine pressure catheter
    1. Adequate contraction pattern indicators
      1. Montevideo units >50 mmHg per contraction
      2. Montevideo units 200-300 mmHg per 10 minutes
    2. Observe for signs of hyperstimulation
      1. Fetal Distress
      2. Tetanic contractions

XI. Efficacy: Labor Induction

  1. Low-risk Nulliparous women may benefit from Labor Induction >39 weeks gestation if ripe Cervix
    1. ACOG Guidance
      1. https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2018/08/clinical-guidance-for-integration-of-the-findings-of-the-arrive-trial
    2. Grobman (2018) N Engl J Med 379(6): 513-23 [PubMed]
    3. Middleton (2018) Cochrane Database Syst Rev (5): CD004945 [PubMed]

XII. Efficacy: Labor Augmentation

  1. Oxytocin (Pitocin) is preferred in PROM
    1. Oral Mifepristone less effective, more side effects
    2. Wing (2005) Am J Obstet Gynecol 192:445-51 [PubMed]
  2. High dose Oxytocin Augmentation in Nulliparous women
    1. As of 2019, studies show no benefit in reduced labor time or reduced cesarean rate
      1. Low dose protocol is preferred as just as efficacious as high dose, with less tachysystole
      2. Prichard (2019) J Matern Fetal Neonatal Med 32(3): 362-8 [PubMed]
      3. Budden (2014) Cochrane Database Syst Rev (10): CD009701 [PubMed]
    2. Early studies suggested decreased labor duration by 2 hours without added risk
      1. Merrill (1999) Obstet Gynecol 94:455-63 [PubMed]
  3. Birth pool as effective as Oxytocin Augmentation
    1. Less pain and less use of epidural analgesia
    2. Cluett (2004) BMJ 328:314-8 [PubMed]

XIII. References

  1. LeFevre (2021) Am Fam Physician 103(2): 90-6 [PubMed]
  2. Wheeler (2022) Am Fam Physician 105(2): 177-86 [PubMed]

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