labor%20induction
LABOR INDUCTION
Labor induction is when an external agent is employed to stimulate contractions before the onset of spontaneous labor.
Labor augmentation uses the same techniques as labor induction but uterine contractions (frequency, duration and strength) are enhanced once labor has started.
Labor induction is generally indicated when the benefits of delivery outweigh the risks of continuing the pregnancy.
Women at 42 weeks of gestation who chose not to undergo labor induction should be monitored more often with at least twice-weekly assessment of fetal well-being (cardiotocography & estimation of maximum amniotic pool depth by ultrasound).

Diagnosis

Indications

  • It is generally indicated when the benefits of delivery outweigh the risks of continuing the pregnancy and there is no contraindication to vaginal delivery
  • Women at 42 weeks of gestation who chose not to undergo labor induction should be monitored more often with at least twice-weekly assessment of fetal well-being (cardiotocography and estimation of maximum amniotic pool depth by ultrasound)

Prolonged Pregnancy

  • Pregnancy that has extended beyond 42 weeks of gestation; also called postterm pregnancy
  • To avoid risks of prolonged pregnancy, women with uncomplicated pregnancies should usually be offered induction of labor between 41 and 42 weeks but it is recommended that they be given every chance to go into spontaneous labor
  • Perinatal mortality and morbidity is increased in pregnancies > 42 weeks
  • Routine induction of labor after 41 weeks reduces perinatal mortality without an increase in cesarean section (CS) rates in women with uncomplicated pregnancy

Preterm Prelabor Rupture of Membranes (PPROM)

  • Rupture of amniotic membranes before 37 weeks of gestation
  • If PPROM occurs before 34 weeks of gestation, induction should not be done unless indicated (eg infection or fetal compromise)
  • If PPROM occurs after 34 weeks of gestation, the decision is made based on the following factors:
    • Maternal risks: Sepsis, possible need for CS
    • Fetal risks: Sepsis, problems associated with preterm birth
    • Access to neonatal intensive care facilities

Prelabor Rupture of Membranes at Term (PROM)

  • Rupture of membranes before the onset of labor in women at or over 37 weeks of gestation
  • Infections of the amniotic cavity and/or lower genital tract are one of the most common causes of PROM (eg Group B Streptococcus)
  • Risks include maternal and neonatal infection, prolapsed cord and fetal distress requiring operative delivery and resulting in low APGAR score
    • Induction of labor can reduce the incidence of infection
  • Risk of infection increases as the interval between rupture and onset of labor increases
    • In term PROM, most women go into spontaneous labor within 24 hours from rupture
    • Induction of labor is recommended approximately 24 hours after PROM
    • Expectant management of women with PROM should not be >96 hours after rupture

Special Circumstances

Previous Cesarean Section (CS)

  • Patients who have undergone CS before may be allowed to have induction of labor (eg CS or expectant management) depending on the clinical scenario and the patient’s wishes
  • Women should be made aware of the risks involved such as uterine rupture or the need for emergency CS

Maternal Request Before 41 weeks

  • Elective induction of labor in women who want an increased feeling of safety, desire to shorten the duration of pregnancy or for other emotional, psychological or social reasons
  • Labor induction should not be routinely offered based on maternal request alone
  • Option is considered where resources allow, patient has favorable cervix, a well-dated pregnancy and there are valid psychological or social reasons for the request

Intrauterine Fetal Death (IUFD)

  • If IUFD occurs in a woman with membranes intact and without evidence of infection or bleeding, either an immediate induction of labor or expectant management could be done
  • If IUFD occurs in a woman with evidence of membrane rupture, bleeding or infection, immediate induction of labor is recommended
  • Patient who has IUFD plus history of previous CS is at greater risk for uterine rupture; dose of inducing agent (eg prostaglandin) should therefore be reduced

Other indications include:

  • Evidence of fetal compromise, maternal medical conditions (eg chronic hypertension, diabetes mellitus, renal disease, chronic pulmonary disease, antiphospholipid syndrome), antepartum hemorrhage, chorioamnionitis, twin pregnancy >38 weeks without complications, restricted intrauterine growth, oligohydramnios

Contraindications

  • Active genital herpes infection
  • Placenta or vasa previa
  • Umbilical cord prolapse
  • Oblique or transverse fetal lie or footling breech
  • Cephalopelvic disproportion
  • Severe fetal growth restriction with fetal compromise
  • Previous uterine rupture
  • Invasive cervical cancer
  • Previous uterine surgery

Evaluation

  • It is important to confirm the presence of a normal fetal heart rate pattern using electronic fetal monitoring
  • Perform careful exam to assess the following:
    • Gestational age (determined preferably by an ultrasound in the 1st trimester), pelvis, fetal size and presentation, and membrane status
  • Patient should be informed of the risks of labor induction
    • Eg increased rate of operative vaginal delivery, excessive uterine activity, cesarean section (CS) birth, abnormal fetal heart rate (HR), maternal water intoxication, uterine rupture, delivery of preterm infant and possible cord prolapse with artificial membrane rupture
  • The state of the cervix is an important predictor of success of labor and vaginal delivery and helps in the selection of induction method
    Modified Bishop Score
    Cervical Feature Pelvic score
    0 1 2 3
    Dilatation (cm) <1 1-2 2-4 >4
    Length of cervix (cm) >4 2-4 1-2 <1
    Station (cm) -3 -2 -1/0 +1/+2
    Consistency Firm Average Soft -
    Position Posterior Mid/ Anterior - -
  • An unfavorable cervix has been defined as having a Bishop score of ≤6
  • A Bishop score of ≥8 denotes that the cervix is “favorable” or ripe, increasing the chance of a spontaneous labor or successful labor induction

Complications

  • Uterine tachysystole with fetal heart rate changes (formerly uterine hyperstimulation)
    • Tachysystole is >5 uterine contractions in a 10-minute period within 30 minutes
    • Tocolytics are used should this occur during labor induction
  • Failed induction
    • Failure to induce labor after one cycle of treatment [ie two vaginal Prostaglandin E2 (PGE2) tabs or gel every 6 hours or one PGE2 controlled-release pessary over a 24-hour period]
    • Assess maternal and fetal well-being and provide support
    • Options include cesarean section (CS) or a further attempt at labor induction depending on the clinical situation and patient’s wishes
  • Uterine rupture
    • The baby should be delivered via emergency CS if uterine rupture occurs during labor induction
  • Cord Prolapse
    • Reduce chance of cord prolapse by assessing the engagement of the presenting part, palpating for the umbilical cord presentation during initial vaginal exam and avoiding amniotomy if the baby’s head is high
    • Check for any signs of low-lying placental site prior to membrane sweeping and labor in


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