ACOG PRACTICE BULLETIN

1 CLINICAL MANAGEMENT GUIDELINES FOR OBSTETRICIAN GYNECOLOGISTSNUMBER 107, AUGUST 2009 Replaces PRACTICE BULLETIN Number 10, November 1999; Committee Opinion Number 228, November1999; Committee Opinion Number 248, December 2000; Committee Opinion Number 283, May 2003 This PRACTICE BULLETIN was devel-oped by the ACOG Committee onPractice Bulletins Obstetrics withthe assistance of Mildred Ramirez,MD, and Susan Ramin, MD. Theinformation is designed to aid prac-titioners in making decisions aboutappropriate obstetric and gyneco-logic care. These guidelines shouldnot be construed as dictating anexclusive course of treatment orprocedure. Variations in practicemay be warranted based on theneeds of the individual patient,resources, and limitations unique tothe institution or type of of LaborMore than 22% of all gravid women undergo induction of labor in the UnitedStates, and the overall rate of induction of labor in the United States has morethan doubled since 1990 to 225 per 1,000 live births in 2006 (1).

2 The goal ofinduction of labor is to achieve vaginal delivery by stimulating uterine con-tractions before the spontaneous onset of labor. Generally, induction of laborhas merit as a therapeutic option when the benefits of expeditious delivery out-weigh the risks of continuing the pregnancy. The benefits of labor inductionmust be weighed against the potential maternal and fetal risks associated withthis procedure (2). The purpose of this document is to review current methodsfor cervical ripening and induction of labor and to summarize the effectivenessof these approaches based on appropriately conducted outcomes-basedresearch. These PRACTICE guidelines classify the indications for and contraindi-cations to induction of labor, describe the various agents used for cervicalripening, cite methods used to induce labor, and outline the requirements for thesafe clinical use of the various methods of inducing labor.

3 BackgroundIn 1948, Theobald and associates described their use of the posterior pituitaryextract, oxytocin, by intravenous drip for labor induction (3). Five years later,oxytocin was the first polypeptide hormone synthesized by du Vigneaud andassociates (4). This synthetic polypeptide hormone has since been used to stim-ulate uterine contractions. Other methods used for induction of labor includemembrane stripping, amniotomy, nipple stimulation, and administration ofprostaglandin E RipeningThe goal of cervical ripening is to facilitate the process of cervical softening,thinning, and dilating with resultant reduction in the rate of failed induction andACOGPRACTICE BULLETINTHE AMERICAN COLLEGE OFOBSTETRICIANS ANDGYNECOLOGISTSWOMEN S HEALTH CARE PHYSICIANS2 ACOG PRACTICE BULLETIN No. 107induction to delivery time. Cervical remodeling is a crit-ical component of normal parturition. Observed changesnot only include collagen breakdown and rearrangementbut also changes in the glycosaminoglycans, increasedproduction of cytokines, and white blood cell infiltration(5).

4 If induction is indicated and the status of the cervixis unfavorable, agents for cervical ripening may be status of the cervix can be determined by the Bishoppelvic scoring system (Table 1) (6). An unfavorable cer-vix generally has been defined as a Bishop score of 6 orless in most randomized trials. If the total score is morethan 8, the probability of vaginal delivery after laborinduction is similar to that after spontaneous labor. Effective methods for cervical ripening include theuse of mechanical cervical dilators and administration ofsynthetic prostaglandin E1(PGE1) and prostaglandin E2(PGE2) (7 10). Mechanical dilation methods are effec-tive in ripening the cervix and include hygroscopic dila-tors, osmotic dilators (Laminaria japonicum), Foleycatheters (14 26 F) with inflation volume of 30 80 mL,double balloon devices (Atad Ripener Device), andextraamniotic saline infusion using infusion rates of30 40 mL/h (11 19).

5 Laminaria japonicumripens thecervix but may be associated with increased peripartuminfections (7, 20). In women undergoing induction withan unfavorable cervix, mechanical methods, exceptextraamniotic saline infusion, are associated with adecreased cesarean delivery rate when compared withoxytocin alone (18). Multiple studies have demonstratedthe efficacy of mechanical cervical dilators. There isinsufficient evidence to assess how effective (vaginaldelivery within 24 hours) mechanical methods are com-pared with prostaglandins (18). Advantages of the Foleycatheter include low cost when compared withprostaglandins, stability at room temperature, andreduced risk of uterine tachysystole with or without fetalheart rate (FHR) changes (18, 21). Misoprostol, a synthetic PGE1analogue, can beadministered intravaginally, orally, or sublingually and isused for both cervical ripening and induction of labor.

6 Itcurrently is available in a 100-mcg (unscored) or a 200-mcg tablet, and can be broken to provide 25-mcg or 50-mcg doses. There is extensive clinical experience withthis agent and a large body of published reports support-ing its safety and efficacy when used appropriately. Nostudies indicate that intrapartum exposure to misoprostol(or other prostaglandin cervical ripening agents) has anylong-term adverse health consequences to the fetus in theabsence of fetal distress, nor is there a plausible biologicbasis for such a concern. Although misoprostol currentlyis approved by the Food and Drug Administration(FDA) for the prevention of peptic ulcers, the FDA in2002 approved a new label on the use of misoprostolduring pregnancy for cervical ripening and for the induc-tion of labor. This labeling does not contain claimsregarding the efficacy or safety of misoprostol,nor doesit stipulate doses or dose intervals.

7 The majority of ad-verse maternal and fetal outcomes associated with miso-prostol therapy resulted from the use of doses greaterthan25 mcg. Two PGE2preparations are commercially available:a gel available in a syringe containing mg ofdinoprostone and a vaginal insert containing 10 mg ofdinoprostone. Both are approved by the FDA for cervi-cal ripening in women at or near term. The vaginal insertreleases prostaglandins at a slower rate ( mg/h) thanthe gel. Compared with placebo or oxytocin alone, vagi-nal prostaglandins used for cervical ripening increase thelikelihood of delivery within 24 hours, do not reduce therate of cesarean delivery, and increase the risk of uterinetachysystole with associated FHR changes (22).Methods of Labor InductionOxytocinOxytocin is one of the most commonly used drugs in theUnited States. The physiology of oxytocin-stimulatedlabor is similar to that of spontaneous labor, althoughindividual patients vary in sensitivity and response tooxytocin.

8 Based on pharmacokinetic studies of syntheticTable Scoring SystemFactorScoreDilation (cm)Position of CervixEffacement (%)Station*Cervical Consistency0 ClosedPosterior0 30 3 Firm11 2 Midposition40 50 2 Medium23 4 Anterior60 70 1, 0 Soft35 6 80+1, +2 *Station reflects a 3 to +3 from Bishop EH. Pelvic scoring for elective induction. Obstet Gynecol 1964;24 PRACTICE BULLETIN No. 1073oxytocin, uterine response ensues after 3 5 minutes ofinfusion, and a steady level of oxytocin in plasma isachieved by 40 minutes (23). The uterine response tooxytocin depends on the duration of the pregnancy; thereis a gradual increase in response from 20 to 30 weeks ofgestation, followed by a plateau from 34 weeks of gesta-tion until term, when sensitivity increases (24). Lowerbody mass index and greater cervical dilation, parity, orgestational age are predictors of successful response tooxytocin for induction (25).Membrane StrippingStripping or sweeping the amniotic membranes is com-monly practiced to induce labor.

9 Significant increases inphospholipase A2activity and prostaglandin F2 (PGF2 )levels occur from membrane stripping (26). Strippingmembranes increases the likelihood of spontaneouslabor within 48 hours and reduces the incidence of induc-tion with other methods (27). Although membrane sweep-ing has been associated with increased risk of prelaborrupture of membranes (28), other published systematicreviews, including one with 1,525 women, have not cor-roborated this finding (27). Women who undergo mem-brane stripping may experience discomfort from theprocedure as well as vaginal bleeding and irregular uter-ine contractions within the ensuing 24 hours (27). Thereare insufficient data to guide clinical PRACTICE for mem-brane stripping in women whose group B streptococcusculture is rupture of the membranes may be used as amethod of labor induction, especially if the condition ofthe cervix is favorable. Used alone for inducing labor,amniotomy can be associated with unpredictable andsometimes long intervals before the onset of contrac-tions.

10 There is insufficient evidence on the efficacy andsafety of amniotomy alone for labor induction (29). In atrial of amniotomy combined with early oxytocin infusioncompared with amniotomy alone, the induction-to-deliv-ery interval was shorter with the amniotomy-plus-oxy-tocin method (30). There are insufficient data to guide thetiming of amniotomy in patients who are receiving intra-partum prophylaxis for group B streptococcal StimulationNipple stimulation or unilateral breast stimulation hasbeen used as a natural and inexpensive nonmedicalmethod for inducing labor. In a systematic review of 6trials including 719 women that compared breast stimu-lation with no intervention, a significant decrease in thenumber of women not in labor at 72 hours was noted, butonly in women with favorable cervices (31). None of thewomen had uterine tachysystole with or without FHRchanges, and there were no differences in meconium-stained amniotic fluid or cesarean delivery rates (31).