This article reviews methodologies for induction of labor. Induction is recommended for various obstetrical or maternal medical indications. Labor induction rates have nearly doubled since 1990. 
The uterus includes both the body and the cervix, with the body being composed of smooth muscle and the cervix predominantly collagen. The cervix undergoes dynamic changes during pregnancy and labor, such as shortening, thinning, and dilating. Mechanical and pharmacological methods of induction of labor can be used to make these physiological cervical changes occur.
There are indications for late preterm, early term, late-term, and post-term timing of delivery depending on a patient's obstetrical and medical history. The American College of Obstetricians and Gynecologists (ACOG) has an extensive list of recommendations on the timing of delivery, with some of the more common clinical scenarios listed below .
Oligohydramnios with the timing at 36 0/7 to 37 6/7 weeks gestationFetal intrauterine growth restriction, with no abnormal dopplers, with the timing at 38 0/7 to 39 6/7 weeks gestationFetal intrauterine growth restriction, with absent end-diastolic flow, with the timing at 34 0/7 weeks gestationFetal intrauterine growth restriction, with reverse end-diastolic flow, with the timing at 32 0/7 weeks gestationChronic hypertension, not on medications, with the timing at 38 0/7 to 39 6/7 weeks gestationGestational Hypertension with the timing at 37 0/7 weeks gestation or at the time of diagnosis if diagnosed laterPreeclampsia without severe features with the timing at 37 0/7 weeks gestation or at the time of diagnosis if diagnosed laterPreeclampsia with severe features with the timing at 34 0/7 weeks gestation or at the time of diagnosis if diagnosed laterPregestational diabetes, well controlled, with the timing at 39 0/7 to 39 6/7 weeks gestationGestational diabetes, diet or exercise controlled, with the timing at 39 0/7 to 40 6/7 weeks gestationPremature preterm rupture of membranes with the timing at 34 0/7 weeks gestation or at the time of diagnosis if diagnosed laterLate-term with the timing at 41 0/7 to 41 6/7 weeks gestation
Contraindications to labor induction include but are not limited to the following:
Vasa Previa or Placenta PreviaTransverse fetal presentationUmbilical cord prolapseHistory of a prior classical cesarean sectionActive herpes infection or outbreakPrevious myomectomy affecting the endometrium
Two primary methods of induction of labor are mechanical and pharmacological. Cervical ripening agents are utilized primarily when the Bishop score is unfavorable, less than eight, which is described below. Mechanical cervical ripening of the cervix can be done with the use of a Foley catheter or double balloon device (i.e. Cook catheter) placed through the endocervical canal.  Osmotic dilators, Laminaria, and synthetic dilators are also used for cervical ripening and placed in the cervical os. Pharmacological forms of induction include synthetic prostaglandins and synthetic Oxytocin, Pitocin. Prostaglandins are used for cervical ripening. Misoprostol, prostaglandin E1 (PGE1), and Dinoprostol, prostaglandin E2 (PGE2) are used in various doses and routes of administration. Notably, prostaglandins are contraindicated in the third trimester in women with a history of a low transverse cesarean section due to concern for uterine rupture.  Pitocin is administered intravenously in varying dosing regimens. Amniotomy is often used in combination with both mechanical and pharmacological methods of labor induction. Less frequently utilized to induce uterine contractions is nipple stimulation.
An inpatient obstetrical care team includes but is not limited to students, nurses, midwives, residents, obstetricians, anesthesiologists, neonatologists, pediatricians, and lactation services. All individuals work concordantly to create a safe environment for the patient and fetus both during labor and in the postpartum period.
The cervix is evaluated on the characteristics of dilation, station, consistency, effacement, and position using the Bishop scoring system. This scoring is done both during antepartum visits and at the time of induction. A favorable cervix, with a score of eight or more, is likely to result in a vaginal delivery. However, if the score is three or less at the start of the induction, then the chance of successful vaginal delivery is low.  As the health care provider, it is beneficial to review this information with patients.
Before starting an induction, all patients should have consented to the process and understand all benefits, maternal and fetal risks, and alternatives to induction. Some of the risks of induction are similar to that of spontaneous labor, which can include a cesarean section, an operative vaginal delivery, chorioamnionitis, non-reassuring fetal heart rate tracing, and postpartum hemorrhage. Reviewing indications for cesarean section and operative vaginal delivery should be discussed prior to induction. One indication for a cesarean section is a failed induction, where cervical dilation has not progressed or continued, despite the use of medications with or without amniotomy. ACOG recommends administrating Pitocin for 12 to 18 hours after the performance of amniotomy before proceeding with a cesarean section for a failed induction. 
With the consent process and when preparing women for induction, it is encouraged to review the different methods of how to induce labor. As indicated above, there are mechanical and pharmacological methods that can be used as a single agent or in combination. A 2016 published randomized control trial addressed this concept. When evaluating women with a singleton pregnancy in the vertex presentation with a Bishop score of less than six, those who received a combination of induction methods, such as a Foley with Misoprostol or a Foley with Pitocin, had a faster median time to delivery compared to those who received only Misoprostol or a Foley alone. However, when adjusting for further variables, a Foley with Pitocin was not better than a single induction method.  There are additional studies and Cochrane reviews comparing amniotomy alone to mechanical and pharmacological methods of induction.  Regardless of data, it is recommended to discuss with the patient that the induction of labor often requires an amniotomy.
As noted above, cesarean section rates and indications for performing a cesarean section should be reviewed with all patients. There is a strong emphasis on cesarean section rates in the United States both in the medical literature and in the social news. The New England Journal of Medicine (NEJM) recently published the ARRIVE trial that compared cesarean section rates and perinatal outcomes in nulliparous women undergoing elective induction at 39 weeks gestation to expectant management. Results demonstrated that there was a significantly lower cesarean section rate in the induction group and that there was no statistically lower adverse perinatal outcomes too.  This study has received much attention in the obstetrical literature and may potentially change induction practice patterns in the country. There have been additional published works reviewing maternal outcomes, including cesarean section rates, with induction of labor. A retrospective study published in 2013 found a decreased odds of cesarean section in both nulliparous and multiparous women being electively induced between 37 and 40 weeks gestation.  What's more, it was found that women were not at increased risk of third or fourth-degree lacerations or operative vaginal deliveries, regardless of gestational age.  Aside from these two articles, there has been extensive literature published analyzing cesarean section rates in relation to variables such as parity, gestational age, and maternal characteristics.
Women being induced for a specific indication, such as intrauterine growth restriction, may inquire about neonatal risks of induction. The same 2013 retrospective study from California further analyzed neonatal outcomes and found no difference in fetal death, neonatal intensive care unit (NICU) admission or respiratory distress across gestational age or parity. However, other literature that has shown a possible difference in neonatal outcomes for fetuses delivered in the early term period at 37 weeks gestation compared to delivery at 38 or 39 weeks gestation. A 2009 NEJM study reviewed this topic from data at the Eunice Kennedy Shriver National Institute; it was found that there was a higher rate of both respiratory and non-respiratory complications with neonates delivered at 37 weeks via cesarean section compared to those delivered at 38 and 39 weeks. Of note, many of the deliveries were elective rather than indicated and cesarean sections were included in the analysis.  In general, for all women being induced, it is important to have a thorough consent process that reviews methods of induction, indications for cesarean section, and maternal and fetal outcomes associated with induction of labor.
As part of the induction process, mechanical dilation with a Foley catheter, a double balloon catheter, or laminaria can be done. A Foley catheter is thread through the external os and internal os. The balloon is then inflated, between 30 milliliters (mL) to 80mL with normal saline, and the balloon places pressure on the internal os to help with cervical dilation.  A 2012 American Journal of Obstetrics and Gynecology (AJOG) article demonstrated that an 80mL inflation volume resulted in a faster induction and less need for Pitocin compared to a volume of 30mL.  With the double balloon, there is one balloon applying pressure to the internal os and there is a second balloon applying pressure to the external os. Both balloons can be filled with different volumes of normal saline. Whether a Foley or a Cook catheter is used, both devices are generally removed once cervical dilation is 4 centimeters (cm) to 5cm. Osmotic dilators are available in different sizes and placed into the cervical os. All dilators should be accounted for when initially placing and when removing during induction.
For cervical ripening with Misoprostol, there is a range of doses as well as routes of administration, such as orally, vaginally, or sublingually. Doses of misoprostol range from 25 micrograms (mcg) to 50mcg.  If induction is planned in the setting of intrauterine fetal demise in the second trimester, ACOG supports higher doses of prostaglandins such as 400mcg every three hours for a maximum of five doses.  PGE2 is available as a vaginal insert and gel formulation. The gel formulation, Prepidil, is 0.5 milligrams (mg), and the insert, Cervidil, is 10mg.  Further pharmacological methods include Pitocin, which is administered intravenously in varying dosing regimens.  Dosing is often titrated so that contractions are two to three minutes apart to cause cervical dilation. Hospitals may have policies on the maximum dose of Pitocin used for patients who are undergoing a trial of labor after cesarean section. Amniotomy with an Amnio Hook can be performed any time the cervix is dilated and is done based on the provider’s discretion. Factors that are taken into account prior to amniotomy include but are not limited to the fetal station, fetal head engagement, patient’s preference, and pain level at the time of amniotomy.
There are risks and complications that can occur during the induction of labor. As stated above, many of these risks can also occur with spontaneous labor. Pharmacological induction can cause uterine tachysystole, with more than five contractions in a ten minute period. Tachysystole may lead to fetal decelerations or fetal bradycardia; much literature has been published regarding the risks of uterine tachysystole with prostaglandins.  As discussed above, cesarean section is always a possibility and must be addressed with patients, along with indications for proceeding with a cesarean section, such as a failed induction of labor or a non-reassuring fetal heart rate tracing. These risks and complications of induction are ideally addressed during the consent process. Further complications or risks include intrapartum vaginal bleeding, presence of meconium-stained amniotic fluid, umbilical cord prolapse, pain not relieved with regional anesthesia, perineal lacerations, postpartum hemorrhage, chorioamnionitis, and postpartum endometritis. 
Induction of labor represents an opportunity to intervene in an ongoing pregnancy with the intent to influence delivery timing for either maternal or fetal benefit. Much literature has been published and continues to be published on both the maternal and fetal safety of induction of labor, especially as it relates to cesarean section rates.
The induction of labor should involve a coordinated team approach involving the obstetrical provider, specialty trained obstetric nurse, anesthesia staff, and a neonatology team. Ultimately whenever there is a change in a patient's status or fetal status, a collaborative effort between all healthcare team members needs to be done to ensure safety for the patient and fetus.
Depending on the acuity level of the facility, continuous electronic fetal monitoring is often done during labor. Many healthcare systems require regular documentation of the electronic fetal heart rate and tocometer as well as notations written for the performance of resuscitative interventions in the presence of a Category II or III fetal heart rate tracing. Nursing should alert obstetrical providers and anesthesia staff about potential concerns and the possibility of proceeding with either an operative vaginal delivery or cesarean section depending on the patient's labor stage and fetal heart rate tracing.
Most hospitals have policies or protocols surrounding the induction of labor, medication administration, fetal heart rate monitoring, oral intake during inductions, pain control, vital sign assessments, and emergencies. As noted above, fetal heart rate should be monitored, along with the contraction pattern, and adequacy of contractions if an intrauterine pressure catheter is present. Electronic medical records often have flowsheets and checklists available for nurses to record events during admission and induction. Depending on the patient's medical history, such as a hypertensive disorder or diabetes (i.e. gestational or pregestational), the hospital may have protocols for the frequency of blood pressure or blood glucose assessments, respectively. Additionally, patients on high-risk medications during induction, such as antihypertensives, Magnesium Sulfate, or insulin, may need more frequent monitoring depending on the hospital's specific protocol. Changes noted by the nurse during these assessments warrants notifying the obstetrical care provider to see if further intervention is required for the patient, such as administration of additional antihypertensives or administering glucose in the setting of hypoglycemia. Other monitoring during induction may include timing of amniotomy and the color of amniotic fluid, which is information that may be beneficial for treatment or management by the obstetrical care provider and neonatal team.
|||ACOG Practice Bulletin No. 107: Induction of labor. Obstetrics and gynecology. 2009 Aug; [PubMed PMID: 19623003]|
|||ACOG committee opinion no. 560: Medically indicated late-preterm and early-term deliveries. Obstetrics and gynecology. 2013 Apr; [PubMed PMID: 23635709]|
|||Caughey AB,Cahill AG,Guise JM,Rouse DJ, Safe prevention of the primary cesarean delivery. American journal of obstetrics and gynecology. 2014 Mar [PubMed PMID: 24565430]|
|||Levine LD,Downes KL,Elovitz MA,Parry S,Sammel MD,Srinivas SK, Mechanical and Pharmacologic Methods of Labor Induction: A Randomized Controlled Trial. Obstetrics and gynecology. 2016 Dec [PubMed PMID: 27824758]|
|||Bricker L,Luckas M, Amniotomy alone for induction of labour. The Cochrane database of systematic reviews. 2000 [PubMed PMID: 11034776]|
|||Grobman WA,Rice MM,Reddy UM,Tita ATN,Silver RM,Mallett G,Hill K,Thom EA,El-Sayed YY,Perez-Delboy A,Rouse DJ,Saade GR,Boggess KA,Chauhan SP,Iams JD,Chien EK,Casey BM,Gibbs RS,Srinivas SK,Swamy GK,Simhan HN,Macones GA, Labor Induction versus Expectant Management in Low-Risk Nulliparous Women. The New England journal of medicine. 2018 Aug 9 [PubMed PMID: 30089070]|
|||Darney BG,Snowden JM,Cheng YW,Jacob L,Nicholson JM,Kaimal A,Dublin S,Getahun D,Caughey AB, Elective induction of labor at term compared with expectant management: maternal and neonatal outcomes. Obstetrics and gynecology. 2013 Oct [PubMed PMID: 24084532]|
|||Tita AT,Landon MB,Spong CY,Lai Y,Leveno KJ,Varner MW,Moawad AH,Caritis SN,Meis PJ,Wapner RJ,Sorokin Y,Miodovnik M,Carpenter M,Peaceman AM,O'Sullivan MJ,Sibai BM,Langer O,Thorp JM,Ramin SM,Mercer BM, Timing of elective repeat cesarean delivery at term and neonatal outcomes. The New England journal of medicine. 2009 Jan 8 [PubMed PMID: 19129525]|
|||Gu N,Ru T,Wang Z,Dai Y,Zheng M,Xu B,Hu Y, Foley Catheter for Induction of Labor at Term: An Open-Label, Randomized Controlled Trial. PloS one. 2015 [PubMed PMID: 26322635]|
|||ACOG Practice Bulletin No. 135: Second-trimester abortion. Obstetrics and gynecology. 2013 Jun [PubMed PMID: 23812485]|