Laurie Barclay, MD
Authors and Disclosures
July 23, 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.
As a proposed performance measure, the guidelines authors suggest that the percentage of patients in whom gestational age is established by clinical criteria when labor is induced for logistic or psychosocial indications.
"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.
Authors and Disclosures
Laurie Barclay, MD
Laurie Barclay, MD, is a freelance writer and reviewer for Medscape.
Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.