INDUCTION AND AUGMENTATION OF LABOR

I. Indications

  1. Preeclampsia
  2. PROM
  3. Chorioamnionitis
  4. Abruptio Placentae
  5. Fetal jeopardy (IUGR, isoimmunization, etc.)
  6. Fetal demise
  7. Post-term pregnancy
  8. For elective induction, ACOG recommends one of the following:
    1. Fetal heart tones by Dopples at least 30wks previously
    2. Fetal heart tones by nonelectronic fetoscopy at least 20wks previously
    3. Positive pregnancy test at least 36wks previously
    4. Ultrasound at 6-12wks supporting EGA of at least 39wks
    5. Ultrasound at 13-20wks, clinical history, and physical exam supporting a gestational age of at least 39wks
    6. Documented fetal lung maturity

II. Contraindications

  1. Placenta previa or vasa previa
  2. Transverse fetal lie
  3. Prolapsed umbilical cord
  4. Prior classical c/s or other transfundal uterine surgery
  5. Active genital HSV
  6. Situations "not contraindications but to necessitate special attention" (per ACOG):
    1. Prior low-transverse c/s
    2. Breech presentation
    3. Maternal heart disease
    4. Multifetal pregnancy
    5. Polyhydramnios
    6. Presenting part above the pelvic inlet
    7. Severe maternal hypertension
    8. Abnormal fetal heart rate patterns not necessitating emergent delivery

III. Risks

  1. Failure of induction
  2. Uterine rupture
  3. Compromised uteroplacental perfusion b/c of uterine hyperstimulation
  4. Cesarian section for nonreassuring fetal heart rate
  5. Amniotic fluid embolism (RR about 2 in one retrospective study of induced singleton births, though absolute risk was very low (Lancet 368:1444, 2006--JW)

IV. Confirming fetal maturity

  1. ACOG says that amniocentesis to confirm fetal maturity is not necessary only if:
    1. FHT by doppler detected at least 30wks prior
    2. Positive pregnancy test at least 36wks prior
    3. Ultrasound at 6-11 wks suggests maturity
    4. Ultrasound at 12-20 wks confirms maturity calculated by LMP

V. "Sweeping the membranes"

  1. Describes a procedure consisting of Inserting an examining finger as high as possible in the cervical os and moving the amniotic membrane off the lower pole of the uterus with a complete circular sweep (one clockwise and one counterclockwise).
  2. Intended to stimulate labor in women with intact membranes at term.
  3. In a study in 264 women with singleton fetuses in cephalic presentation at term, about to undergo labor induction, randomized to sweeping of membranes vs. no sweeping, those undergoing sweeping had sig. higher incidence of spontaneous vaginal delivery (69% vs. 56%), shorter mean interval from induction to delivery (14h vs. 19h), and less likelihood of receiving oxytocin during labor (46% vs. 59%) (Obs. Gyn. 107:569, 2006--JW)

     

V. Cervical ripening--Indicated when inducation is indicated but cervix is unfavorable (e.g. if Bishop's Score < 8)

  1. Prostaglandin E2 (Dinoprostone)
  1. May repeat dose x 1 6-12h after initial dose
  2. May stimulate contractions
    1. When contractions occur, us. start within 1h and peak in < 4h
    2. May cause hyperstimulation (> 5ctx/10min for total 20min)
      1. Occurs in 1% for intracervical gel and 5% for intravaginal gel
      2. If occurs, tx with IV or SQ terbutaline
      3. Irrigation of cx/vagina is not helpful
  3. Other side effects (uncommon)
    1. Fever
    2. Vomiting
    3. Diarrhea
  4. Contraindications
    1. Use with caution (esp. forms other than Cervidil) in pts with h/o prior c/s
    2. Don't use if having regular uterine contractions (risk of uterine hyperstimulation)
    3. Glaucoma (relative)
    4. Severe hepatic or renal impairment (relative)
    5. Asthma (relative)
  5. Guidelines for administration (ACOG)
    1. Have pt remain recumbent for 30min after administration
    2. Monitor FHR before and for 30min-2h after administration, longer if having contractions
      1. If using the sustained-release vaginal insert, monitor FHR until 15min after it is removed; remove at onset of labor
    3. Monitor maternal VS
    4. Don't start Oxytocin until 6-12h after administering gel OR 30-60min after removal of sustained-release vaginal insert (Cervidil)
  6. Different forms
    1. Intravaginal gel 2-5mg (locally compounded by hosp. pharmacy)
    2. Intracervical gel 0.5mg (locally compounded by hosp. pharmacy)--intracervical route may be more efficacious with very unripe cervices and cause less uterine stimulation than the vaginal route
    3. Prepidil (0.5mg dinoprostone intracervical gel in 2.5cc)--MAXIMUM 3 DOSES IN ANY 24h PERIOD
    4. Cervidil (10mg dinoprostone sustained-release vaginal insert) --slower release of medication than intravaginal gel; unlike the other products, can be removed should hyperstimulation occur, but higher incidence of hyperstimulation
    5. Comparisons among these
      1. IN a trial in 63 pts admitted for induction at > 36wks with Bishop score < 6 and cervical dilation 2cm or less, randomized to PGE2 placed intracervically or in posterior fornix, time to onset of labor and median time to delivery were not sig. diff. in the two groups, though among the pts who only required one dose, there was sig. lower time to delivery with intracervical administration (11.7h vs. 16.2h) (Obs. Gyn. 103:13, 2004--AFP)
  1. Mechanical dilation
    1. Atad Ripener Device
    2. Osmotic cervical dilators (Laminaria japonicum & various synthetic dilators)--may be ass'd with increased risk of peripartum infection
    3. Foley catheter (16F) inserted into endocervical canal, then inflating the bulb w/30cc of sterile water, with gentle traction aplied and induction initiated after extrusion of the catheter
      1. In a retrospective study of use of this method vs. pharmacologic cervical ripening in 126 women, incidence of preterm delivery with the following pregnancy was no different based on method of cervical ripening (there had been concern that the Foley method would cause cervical trauma and predispose to subsequent preterm delivery) (Am. J. Obs. Gyn. 190:751, 2004--AFP)
  2. Misoprostol (PGE1) intravag or 25 ug PO Q6h has been used for this (see below)
    1. Has been ass'd with uterine hyperstimulation, uterine rupture, and increased incidence of meconium staining of amniotic fluid
  3. Emerging methods as of 2005--Vaginal recombinant human relaxin, intracervical porcine relaxin

VI. "Stripping" of membranes--may reduce need for induction BUT may be ass'd with risk of infection, bleeding from undx'd placenta previa, or accidental rupture of membranes.

VII. Amniotomy--When combined w/Oxytocin, reduces duration to delivery; can be ass'd with cord prolapse, chorioamnionitis, and rupture of vasa previa. ALWAYS FEEL FOR CORD before doing amniotomy and avoid dislodging the fetal head

VIII. Induction with Oxytocin

  1. ACOG recommends fetal monitoring "similar to that recommended for high-risk pts in active labor"
  2. "Bishop's Score" often used to predict success of induction
  3. Pharmacology
    1. Usually given in solution of 10-20U in 1000ml
    2. Usually start at 0.5-2mU/min and increase 1-2mU/min Q15-40min; max 20-40mU/min
    3. "High dose" regimens have been used that start at 6mU/min and increase by 6mU/min Q15-30min (ass'd with shorter labors and less risk of chorioamnionitis or c/s for dystocia, but increased risk of hyperstimulation)
    4. Usual dose requirement to attain 3-5 ctx/10min is 5-25mU/min
    5. Uterine response occurs 3-5min after administration
    6. Plasma steady-state is reached about 40min after dose change
    7. Stop the pit if:
      1. > 7 contractions/15min
      2. IUPS shows > 15-20mm Hg between contractions
      3. Fetal heart rate abnormalities occur
  4. Risks
    1. Uterine hyperstimulation or high resting tone (> 20mm Hg between ctx) can compromise uteroplacental flow--Monitor fetal heart rate while pt on it
    2. Uterine rupture
    3. Abruptio placentae
    4. Hyponatremia (b/c of ADH-like properties of Oxytocin; us. only seen w/prolonged administration of > 40mU/min)
    5. Maternal hypotension (only with rapid IV infusion)--Monitor maternal HR while pt on it

IX. Induction with Misoprostol

  1. 130 women for induction randomized to receive induction by IV oxytocin or 100ug misoprostol intravag Q4h until labor was established. Misoprostol group at the outset had lower Bishop scores on average. However, median induction-to-delivery time sig. shorter (about 9.5 vs. 14.5h). Epidurals used more frequently in women receiving oxytocin (73% vs. 50%). No diff. in incidence of c/s. "Uterine tachysystole" sig. more common in misoprostol group (70% vs. 11%) (Obs. Gyn. 89:387, 1997)
  1. Misoprostol PO vs. Intravaginal--206 women at at least 37wks were randomized to Misoprostol 50mg PO vs. 50mg intravag; tx given Q4h until either (3 ctx Q10min or spontaneous ROM or concerning FHR pattern or other complications or delivery). Vaginal group had nonsig. higher rates of uterine tachysystole and hyperstimulation and sig. lower mean time to delivery (846min vs. 1072min). No diff. in use of epidurals or oxytocin or rates of c/s or assisted delivery, or neonatal outcomes (Obs. Gyn. 92:481, 1998--AFP)
  1. Misoprostol intravag vs. Oxytocin IV for induction for PROM at term
    1. 197 women with PROM at mean 38wks randomized to intravaginal misoprostol (25ug in posterior fornix); repeat after 6h if not in adequate contraction pattern) vs. IV oxytocin (up to 20mU/min) for labor induction.  No sig. diff. in rates of vaginal delivery within 24h (76% w/misoprostol vs. 74% with oxytocin), total duration from induction to delivery, intra-amniotic infection, neonatal sepsis, and c/s (Am. J. Obs. Gyn 179:94, 1998--AFP)
    2. 108 women with PROM at > 37wks gestation not in active labor randomized to misoprostol 50ug PO Q4h vs. IV oxytocin; oxytocin group had sig. lower time to delivery (501 minutes vs. 720 minutes) (Obs. Gyn. 94:994, 1999--AFP)
  2. May be ass'd with higher risks of uterine rupture in VBAC than oxytocin inductionS

X. Influence of time of day in induction outcomes

  1. In a study in 620 women at 36-42wks gestation with cephalic presentation scheduled for prostaglandin induction randomized to admission at 8am vs. 8pm, there was no sig. diff. in primary outcomes of delivery within 24h, uterine hyperstimulation with adverse FHR changes, or c/s, but morning-admission women had sig. lower incidence of requiring oxytocin (45% vs. 54%) and among nullips, sig. lower incidence of operative vaginal birth (16% vs. 34%) (Obs. Gyn. 108:350, 2006--abst)

XI. For fetal demise--If remote from term, Oxytocin will be less effective; better if the cervix is ripened first.