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What is induction of labor?

Induction of labor is the use of medications or other methods to start uterine contractions before the natural onset of labor in order to have a vaginal delivery.

Why is induction of labor done?

Induction of labor is usually considered when continuing the pregnancy would increase  the risks to the baby or mother  without giving any benefit to either.

Some Medical Reasons for Induction [1-3]

Nonmedical (Elective) Reasons for Induction

  • The mother is uncomfortable or anxious
  • Partner soon leaving town (including  military deployment)
  • Family in town
  • The mother has rapid deliveries.
  • Mother lives a long distance from the hospital,
The National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, and American College of Obstetricians and Gynecologists recommend[4]
  • Labor induction should be performed only for medical indications
  • If done for nonmedical indications, the gestational age should be 39 weeks or more, and the cervix should be favorable (Bishop score 8 or higher), especially in a woman who has never given birth (nulliparous).
  • Cervical ripening may be considered when there is a medical indication for induction.
  • Since inductions without medical indication should not be done with an unripe cervix, cervical ripening would not be an option

What is a Bishop Score and what is a favorable (ripe) or an unfavorable (unripe) cervix?

The Bishop Score (also known as Pelvic Score) is the most commonly used method to assess the readiness of the cervix for induction of labor. The Bishop Score gives points to 5 components of the pelvic examination dilation, effacement of the cervix, station of the fetus, consistency of the cervix, and position of the cervix.


0 1 2
Dilation (cm)


1-2 cm


5 -6 cm 

Effacement (%)








-1 or 0

+1, +2 





Position Posterior Mid Anterior
  • If the Bishop score is 8 or greater the chances of having a vaginal delivery are good and the cervix is said to be favorable or "ripe" for induction.

  •  If the Bishop score is 6 or less the chances of having a vaginal delivery are low and the cervix is said to be unfavorable or "unripe" for induction.

See Bishop Score Calculator for more on the Bishop Score

What is cervical ripening?

Cervical ripening is the process where the cervix becomes ready for labor by becoming softer , thinner and opening (dilating) during the last few weeks of pregnancy. Medications or mechanical dilators are sometimes used to artificially ripen the cervix  before induction to make the cervix more favorable and a vaginal delivery more likely.

What are some methods that are used to ripen the cervix?[1, 7-16, 30]

  • Medications prostaglandin E1 (PGE1) and  prostaglandin E2 (PGE2)
    • Misoprostol (PGE1) can be given by mouth or placed in the vagina.
    • Dinoprostone (PGE2 ) available as a gel and a vaginal insert that is placed in the vagina.

    Prostaglandins are hormones produced by most tissues of the body including the amniotic membranes and cervix. Prostaglandins cause the cervix to soften and relax. Prostaglandins can also cause the uterus to contract.

  • Mechanical devices
    • Foley catheter (14–26 F) with inflation volume of 30–80 mL
    • Double balloon devices (Atad Ripener Device)
    • Osmotic dilators (Laminaria and Dilapan-S)

    Mechanical devices put pressure on the cervix causing the release of prostaglandins which cause the cervix to soften and open. [29]

What are some methods that  can be used to induce labor? [1]

  • Oxytocin is a hormone that is made in the brain and causes the uterus to contract  Oxytocin  is released naturally  into the blood during labor, nipple stimulation, and sex. Synthetic oxytocin (Pitocin)  is used to begin or stimulate labor [6]

  • Amniotomy also known as artificial rupturing of the membranes (AROM) or breaking your water. The procedure is sometimes  done using a plastic device that looks like a crochet needle (AmniHook® ) to open the water bag that surrounds the baby.  Amniotomy used alone for inducing labor can be unpredictable . Amniotomy is more effective in speeding up the progress of labor when used with oxytocin. [31,32]

What are the risks of inducing labor?

  • The induction may fail and you will need to be delivered by cesarean section.

  • Failed induction was found to be more likely with an unfavorable cervix in a woman who has never given birth (nulliparous) in some but not all studies [37].
    The NICHD, SMFM, and ACOG recommend
    "The diagnosis of failed induction should only be made after an adequate attempt. Failed induction is defined as failure to generate regular (eg, every 3 minutes) contractions and cervical change after at least 24 hours of oxytocin administration, with artificial membrane rupture if feasible."
  • Abnormal contraction pattern.
    Prostaglandins and oxytocin may cause contractions that last too long are too strong or are too close together.  The abnormal contractions can cause  your baby's heart rate to drop.

  • Cord prolapse [33]
    The umbilical cord is the tube-like structure attached to your developing baby's belly that supplies nutrients and oxygen to your baby. Sometimes after the membranes have ruptured the baby's umbilical cord may pass through the cervix (the opening of the uterus) in front of the head or body of your baby. This called cord prolapse.  Pressure on the umbilical cord can decrease the blood flow to the baby causing the baby's heart rate to drop. 

  • Bleeding and Pain [34]
    Bleeding and pain may be caused by mechanical methods such as the foley  catheter or dilators.
  • Infection
    An increased risk for maternal and neonatal infections has been reported in connection with the use  mechanical devices
  • Uterine Rupture [17,18]
    Uterine rupture is a tear through the entire thickness of the uterine wall. Uterine rupture usually occurs in a woman who has had an operation on her uterus such as a cesarean section, myomectomy (removal of fibroids) , or metroplasty (repair of uterine malformation).  Although uterine rupture may occur  even with natural labor the chances of uterine rupture occurring  iare greater if  prostaglandins are used to induce labor.

  • Amniotic Fluid Embolism [19-21]
    Amniotic fluid embolism (AFE ) is a rare unpredictable condition in which amniotic fluid , the fluid around the baby, enters the mother's blood stream and causes heart and lung failure with uncontrolled bleeding. AFE has been associated with advanced maternal age, polyhydramnios, cervical laceration, uterine rupture, placenta previa , abruption, eclampsia, fetal distress , cesarean delivery, and in some studies induction of labor.

Can you be induced if you are having a vaginal birth after cesarean delivery (VBAC)?[22-36]

Induction of labor for medical reasons may be an option for women who wish to attempt a vaginal birth after having had a cesarean delivery (VBAC) . If you are attempting a VBAC you should know that you are more likely to have a cesarean section with induction of labor.  In addition induction of labor with oxytocin or prostaglandins has been associated with an increased risk of uterine rupture in women attempting VBAC in some studies.  ACOG recommends "Misoprostol should not be used for third trimester cervical ripening or labor induction in patients who have had a cesarean delivery or major uterine surgery." The Society of Obstetricians and Gynaecologists of Canada. (SOGC) considers cervical ripening with a transcervical foley catheter a safer option in women planning VBAC.  However, the risk of uterine rupture is not entirely eliminated with the use of the Foley catheter .

More Questions

Reviewed by Mark Curran, M.D. FACOG

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7. Cytotec (misoprostol) tablet
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