July 24, 2009 — On July 21, the American College of Obstetricians and Gynecologists (ACOG) issued revised guidelines on when and how to induce labor in pregnant women. The updated recommendations are published as a Practice Bulletin, “Induction of Labor,” in the August issue of Obstetrics & Gynecology. The bulletin aims to guide physicians regarding their choice of induction methods that may be most suitable in specific settings and to elucidate the safety requirements, risks, and benefits of various regimens to induce labor.
Benefits vs Risks of Labor Induction
For the last 2 decades, the rate of labor induction in the United States has more than doubled, with more than 22% of all pregnant women in 2006 having labor induced. This increase in use necessitates a careful review of indications, risks, and benefits.
The goal of labor induction is to stimulate uterine contractions before the spontaneous onset of labor, resulting in vaginal delivery. The benefits of labor induction must be weighed against the potential maternal and fetal risks associated with this procedure. When the benefits of expeditious delivery are greater than the risks of continuing the pregnancy, inducing labor can be justified as a therapeutic intervention.
“There are certain health conditions, in either the woman or the fetus, where the benefit of inducing labor is clear-cut,” coauthor Susan Ramin, MD, from the University of Texas Medical School in Houston, said in a news release. “And, there are some nonmedical situations in which induction also may be prudent, for instance, in rural areas where the distance to the hospital is just too great to risk waiting for spontaneous labor to happen at home.”
Recommendations Based on Sound Evidence
Based on evidence from methodologically sound outcomes-based research, the bulletin attempts to review current methods for cervical ripening and for inducing labor and to summarize the efficacy of these approaches. Also highlighted are indications for and contraindications to inducting labor, pharmacologic characteristics of various agents used for cervical ripening, regimens used for labor induction, and the requirements for safe clinical use of these techniques.
The bulletin authors searched the MEDLINE database, the Cochrane Library, and ACOG’s own internal resources and documents to identify pertinent English-language articles published between January 1985 and January 2009. Although articles reporting results of original research were given priority, review articles and commentaries were also consulted, as were guidelines published by organizations or institutions such as ACOG and the National Institutes of Health. However, abstracts of research presented at symposia and scientific conferences were excluded. Expert opinions from obstetrician-gynecologists were used when reliable research evidence was not available.
Indications for Labor Induction
Possible indications for labor induction may include gestational or chronic hypertension, preeclampsia, eclampsia, diabetes, premature rupture of membranes, severe fetal growth restriction, and postterm pregnancy. However, physicians should decide whether labor induction is warranted on a case-by-case basis, after consideration of maternal and infant conditions, cervical status, gestational age, and other factors.
Contraindications to labor induction include transverse fetal position, umbilical cord prolapse, active genital herpes infection, placenta previa, and a history of previous myomectomy.
When labor induction is deemed necessary, the gestational age of the fetus should be determined to be at least 39 weeks, or there must be evidence of fetal lung maturity.
The first step in labor induction is cervical ripening using drugs or mechanical cervical dilators to dilate the cervix sufficiently before labor is induced. The next step is to induce labor using oxytocin, membrane stripping, rupture of the amniotic membrane, or nipple stimulation.
Misoprostol, which is approved for treatment of peptic ulcers, is often used off-label for cervical ripening as well as for labor induction. In women who have had any previous cesarean delivery, however, inducing labor with misoprostol may increase risk for uterine rupture and should therefore be avoided.
Specific clinical recommendations and conclusions, all based on good and consistent scientific evidence (level A), are as follows:
* For cervical ripening and labor induction, prostaglandin E (PGE) analogues are effective.
* When labor induction is indicated, low-dose or high-dose oxytocin regimens are appropriate.
* Regardless of Bishop score, the most efficient method of labor induction before 28 weeks of gestation appears to be vaginal misoprostol. However, infusion of high-dose oxytocin is also an acceptable option.
* For cervical ripening and induction of labor, an appropriate initial dose of misoprostol is approximately 25 µg, with frequency of administration not to exceed 1 dose every 3 to 6 hours.
* For induction of labor in women with premature rupture of membranes, intravaginal PGE2 appears to be safe and effective.
* In women with previous cesarean delivery or major uterine surgery, the use of misoprostol should be avoided in the third trimester because it has been linked to a greater risk for uterine rupture.
* The Foley catheter is a reasonable, effective option to promote cervical ripening and labor induction.
An additional clinical recommendation, based on limited or inconsistent evidence (level B), is that misoprostol, 50 µg every 6 hours, to induce labor may be appropriate in some situations. However, higher doses are linked to a greater risk for uterine tachysystole with fetal heart rate (FHR) decelerations and other complications.
“A physician capable of performing a cesarean should be readily available any time induction is used in the event that the induction isn’t successful in producing a vaginal delivery,” Dr. Ramin concluded. “These guidelines will help physicians utilize the most appropriate method depending on the unique characteristics of the pregnant woman and her fetus.”
Obstet Gynecol. 2009;114:386-397.
Labor induction occurs in more than 22% of pregnant women in the United States and has doubled in rate between 1990 and 2006, according to Martin and colleagues in the January 7, 2009, issue of National Vital Statistics Reports. Cervical ripening methods include mechanical dilation, synthetic PGE1, and PGE2. Mechanical dilation methods are hygroscopic dilators, osmotic dilators, Foley catheters, double-balloon devices, and extra-amniotic saline infusion. The PGE1 analogue, misoprostol, can be used for cervical ripening and labor induction. PGE2 is available as dinoprostone gel or as a vaginal insert. Methods of labor induction include oxytocin, membrane stripping, amniotomy, and nipple stimulation.
This guideline from the ACOG describes the indications for and contraindications to labor induction, methods for cervical ripening, methods for labor induction, and recommendations for use of these methods.
* Indications for labor induction include abruptio placentae, chorioamnionitis, fetal demise, gestational hypertension, preeclampsia, eclampsia, premature rupture of membranes, postterm pregnancy, maternal medical conditions, and fetal compromise.
* Labor might be induced for logistic reasons if term gestation is confirmed.
* Contraindications to labor induction include vasa previa or complete placenta previa, transverse fetal lie, umbilical cord prolapsed, previous classic cesarean delivery, active genital herpes infection, and previous myomectomy entering the endometrial cavity.
* Criteria for cervical ripening or labor induction are assessment of gestational age and risk to mother or fetus; assessment of cervix, pelvis, fetal size, and presentation; FHR and uterine contraction monitoring; patient counseling; and capability for cesarean delivery.
* PGE analogues are effective methods for cervical ripening and inducing labor.
* An effective alternative for cervical ripening and inducing labor is a Foley catheter, which reduces the duration of labor and risk for cesarean delivery.
* Misoprostol initial dose is 25 µg every 3 to 6 hours intravaginally.
* Misoprostol doses of 50 µg every 6 hours might be indicated but are linked with the risk for uterine tachysystole with FHR decelerations.
* Buccal and sublingual misoprostol for cervical ripening or labor induction are not recommended because of lack of safety data.
* Misoprostol should be avoided in the third trimester in women with prior cesarean delivery or major uterine surgery because of an increased risk for uterine rupture.
* Dinoprostone can be administered intracervically or intravaginally.
* Uterine tachysystole with or without FHR changes occur more commonly with vaginal misoprostol vs vaginal or intracervical PGE2 and oxytocin.
* The management of uterine tachysystole and category III FHR tracing includes maternal repositioning, supplemental oxygen, subcutaneous terbutaline, and decrease or discontinuation of oxytocin.
* Cesarean delivery might be necessary for persistent tachysystole or FHR abnormalities.
* After PGE use, surveillance should include initial continuous FHR and uterine activity monitoring and recumbent position for the pregnant patient.
* Limited data show that outpatient use of intravaginal PGE2 gel for 5 days, controlled-release PGE2, and a Foley catheter appear to be effective and safe.
* Oxytocin for labor induction can be given as low dose (initial 0.5 – 2 mU/minute with incremental increases of 1 – 2 mU/minute) or high dose (initial 6 mU/minute with increases of 3 – 6 mU/minute).
* The maximal oxytocin dose is unknown.
* The main adverse effects of oxytocin are dose-related uterine tachysystole and category II or category III FHR tracings.
* The risks for amniotomy are umbilical cord prolapse, chorioamnionitis, umbilical cord compression, vasa previa rupture, and the risk for vertical transmission of HIV.
* Amniotic membrane stripping risks include bleeding from placenta previa or low-lying placenta and amniotomy.
* Breast stimulation is linked with uterine tachysystole with FHR decelerations and increased trend in perinatal death.
* In women with premature rupture of membranes at term, labor can be induced with oxytocin or PGE, but there are insufficient data on mechanical dilator use.
* Management of intrauterine fetal demise depends on gestational age, uterine scar, and maternal preference.
* For intrauterine fetal demise in the second trimester, dilation and evacuation is an option.
* For intrauterine demise before 28 weeks’ gestational age, misoprostol is the most efficient method; high-dose oxytocin is also an option.
* In pregnant women who require cervical ripening and labor induction, PGE analogues are effective, and the Foley catheter is an effective alternative. Labor can be induced with low-dose or high-dose oxytoxin regimens.
* For intrauterine fetal demise before 28 weeks of gestation, the most efficient method of labor induction is vaginal misoprostol. Misoprostol use should be avoided in the third trimester in women with previous cesarean delivery or major uterine surgery because of a link with an increased risk for uterine rupture.