- Email: [email protected]
Rising rates of labor induction: present concerns and future strategies
CURRENT COMMENTARY
Rising Rates of Labor Induction: Present Concerns and Future Strategies William F. Rayburn, MD, and Jun Zhang, MD, PhD Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, School of Medicine, University of New Mexico, Albuquerque, New Mexico; and Epidemiology Branch, National Institute of Health and Human Development, National Institutes of Health, Bethesda, Maryland
The rate of labor induction nationwide increased gradually from 9.5% to 19.4% between 1990 and 1998. Reasons for this doubling of inductions relate to widespread availability of cervical ripening agents, pressure from patients, conveniences to physicians, and litigious constraints. The increase in medically indicated inductions was slower than the overall increase, suggesting that induction for marginal or elective reasons has risen more rapidly. Data to support or refute the benefits of marginal or elective inductions are limited. Many trials of inductions for marginal indications are either nonexistent or retrospective with small sample sizes, thereby limiting definitive conclusions. Until prospective clinical trials can better validate reasons for the liberal use of labor induction, it would seem prudent to maintain a cautious approach, especially among nulliparous women. Strategies are proposed for developing evidence-based guidelines to reduce the presumed increase in health care costs, risk of cesarean delivery for nulliparas, and overscheduling in labor and delivery. (Obstet Gynecol 2002;100:164 –7. © 2002 by The American College of Obstetricians and Gynecologists.)
Induction of labor is one of the most common procedures in obstetrics. Since 1989, all states and the District of Columbia have used a new standardized certificate of live birth that contains a check box for “induction of labor.” Birth certificate data reported to the National Center for Health Statistics revealed that the rate of labor induction increased gradually from 9.5% to 19.4% for all births between 1990 and 1998.1 These rates varied widely between and within many states. For example, induction rates in 1998 ranged from 10.9% in Hawaii to 41.6% in Wisconsin and from 6.5% to 53.2% in counties of New York. Address reprint requests to: William F. Rayburn, MD, University of New Mexico Health Sciences Center, Department of Obstetrics and Gynecology, 2211 Lomas Boulevard NE (ACC 4), Albuquerque, NM 87131-5286; E-mail: [email protected].
164
Although transfer of information to the birth certificate is potentially fallible, the number of labor inductions now exceeds the combined number of primary cesarean deliveries, vaginal births after cesarean, and operative vaginal deliveries. In the United States, induction rates exceeding 40% of all births may be found at many community hospitals.2 EXPLANATIONS FOR RISING RATES Explanations for this doubling in labor inductions are complex and multifactorial. An improved ability to plan the timing of birth by the physician, patient, and her family is the most common reason. Other explanations include the presence of a very favorable cervix (Bishop score greater than 8) at term, availability of cervical ripeners, more relaxed attitudes toward marginal or elective inductions, and presumed medical liability from continued expectant management. Lastly, pressures by demanding patients or financial gain by the provider are unspoken reasons to induce labor. Indications for induction of labor are not absolute. Examples of maternal or fetal conditions that may be indications include abruptio placentae, premature rupture of membranes, post-term pregnancy, active medical conditions, fetal compromise, and preeclampsia/eclampsia. Better detection has identified pregnancies at risk. For example, borderline hypertensive disorders or an abnormally low volume of amniotic fluid are common indications for induced labor.1 Although inductions for pregnancies with abruptio placentae and multifetal pregnancy are infrequent, their rates have also increased significantly.1 White women are more likely than those of other races to have an induced labor. Maternal age has little impact, except in very young women where induced labor is less common.1 Induction rates are higher with higher formal education and with earlier prenatal care. Nulliparas have a higher induction rate than do multiparas. ELECTIVE OR MARGINAL INDICATIONS Induction of labor has undisputable merit as a therapeutic option when benefits of expeditious delivery clearly outweigh the risks of continuing a pregnancy. Although there is no universally accepted definition, an elective induction is generally accepted to be the absence of maternal or fetal indications. The number of elective inductions has risen rapidly, presumably because in-
VOL. 100, NO. 1, JULY 2002 © 2002 by The American College of Obstetricians and Gynecologists. Published by Elsevier Science Inc.
0029-7844/02/$22.00 PII S0029-7844(02)02047-1
creases of indicated inductions during the past decade were significantly lower than the overall increase (70% versus 100%).1 In some settings, elective inductions comprise up to half of all inductions and at least 10% of all births after excluding repeat cesarean deliveries.2,3 Advocates agree that elective inductions allow for better planning of daytime deliveries with theoretically a less fatigued patient and with more perinatal medical care personnel. A modest increase in instrumental delivery, in part explained by a higher rate of epidural anesthesia, has been found in most but not all studies of elective induction compared with spontaneous labor.3,4 More convincing evidence exists that elective induction at term increases the risk two-fold for a cesarean delivery among nulliparas (14 –20%).2,4 Failure to progress is the primary indication. Because induction of labor is so common, even a small additional risk of cesarean delivery for nulliparous women may translate into a larger number of cesarean deliveries nationwide. It is likely that nulliparous women differ from multiparous women in preinduction cervical effacement and dilatation and in response to ripening methods. Multiparous women generally present with a more inducible cervix. Thus, when compared with spontaneous labor, elective induction at term does not appear to pose an increased risk either to the multiparous woman or to her fetus in carefully selected populations with a very favorable cervix.3 Before the introduction of fetal surveillance techniques, prolonged pregnancy was associated with a twofold to ten-fold increase in perinatal mortality and with a two-fold to four-fold increase in the incidence of fetal distress.3 More recent studies have suggested that, despite costly monitoring techniques, the post-term fetus remains at risk for certain perinatal morbidities such as meconium aspiration, fetal intolerance to labor, and fetal macrosomia. Management of the uncomplicated pregnancy that extends 1 week beyond the estimated date of delivery is controversial. Central to this controversy is whether the fetus is at increased risk of deterioration as gestation continues. In the otherwise uncomplicated post-term pregnancy, there is little difference in perinatal outcome with expectant management compared with immediate induction. The literature does not provide a clear answer as to which management plan should be followed.5 Among pregnancies 41 weeks or longer, the cesarean delivery rate has been reported to be either increased, decreased, or unchanged among women whose labor is induced rather than spontaneous.3–5 Macrosomia, defined as a birth weight exceeding 4000 g, accounts for almost 10% of all births. Two scenarios are relatively common: macrosomia in a prior pregnancy or being suspected in the present pregnancy.
VOL. 100, NO. 1, JULY 2002
Theoretically, an induction of labor to eliminate further fetal growth should reduce the risks of cesarean delivery and of shoulder dystocia with brachial plexus injury. Decision making is complicated by inaccuracies in estimating fetal weight and by the lack of sound scientific support to justify intervention even if the fetal weight estimation is presumably accurate. Labor that is induced rather than spontaneous is associated with increased cesarean delivery rates.3 Independent studies have also reported a higher rate of induction of labor in women whose fetuses later had shoulder dystocia.3 Possible explanations for greater risks of cesarean delivery and shoulder dystocia when labor is induced include differences in labor progression, degrees of fetal head molding, strength of contractions, and more aggressive attitudes of obstetricians. Randomized trials reveal that induction of labor, compared with expectant management, does not significantly decrease the rates of shoulder dystocia and cesarean delivery in nondiabetic and diabetic populations.3–5 Furthermore, clinical trials to determine the risk of birth injury (brachial plexus injury, clavicular fractures) would require very large sample sizes.3– 6 A liberal attitude toward ordering fetal surveillance testing is common at or beyond term. Oligohydramnios (amniotic fluid index 5 or less) is often found in such pregnancies. Risks associated with oligohydramnios include meconium, umbilical cord compression, and subsequent intrapartum fetal heart rate decelerations. Oligohydramnios is considered to be isolated in the absence of hypertension, fetal anomalies, or fetal growth restriction. Induction of labor may not be warranted in cases of isolated oligohydramnios. Fetal tolerance to labor and neonatal outcome measures may not differ between groups with isolated oligohydramnios and those with a normal fluid volume. Conway et al7 reported on 183 women undergoing labor induction for isolated oligohydramnios between 37 and 416⁄7 weeks’ gestation. Compared with a control group with normal amniotic fluid measurements who presented in spontaneous labor, women who were induced had significantly more cesarean deliveries (15.8% versus 6.6%, P ⬍ .01, odds ratio 2.7). This increase of operative delivery in the oligohydramnios group was not attributable to fetal intolerance to labor. Also, fetal risk was not increased among patients who presented in spontaneous labor. Certain indications for labor induction are not validated by prior clinical investigations. Marked maternal physiologic changes of pregnancy requiring maternal treatment for edema, backache, or indigestion may explain why some inductions are undertaken at term. Some indications for induction may have no bearing on the decision to induce labor or might even be relative con-
Rayburn and Zhang
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165
traindications. For example, a desired vaginal birth after cesarean delivery, a prior fetus with shoulder dystocia, or previous cephalopelvic disproportion are not documented indications for induction of labor. PRESENT CONCERNS Scheduling an induction rather than waiting for spontaneous labor offers many advantages: easing domestic arrangements, ensuring attendance of the patient’s physician, and avoiding journeys during labor either from distant places or in severe climatic conditions. Labor inductions for logistic reasons may occur so often, however, that limitations of labor and delivery resources require scheduling several days in advance. Thus, some induction attempts may be scheduled later than the clinician would desire, with many cases undergoing spontaneous labor beforehand. For the obstetrician and nursing staff, there would be value in timing deliveries during the daytime or evening on weekdays. Nursing staff hours could be staggered, so that extra nurses would be on duty at peak hours of postinduction deliveries. Although these arguments are appealing, there are insufficient published data for this practice to be recommended. Induction of labor may bear a stiff price when considering increases in costs related to maternal morbidity and cesarean delivery. Costs for the longer predelivery hospital stay among women with induced rather than spontaneous labor is noteworthy in today’s managed care environment.3 The time required for cervical ripening is important to consider when evaluating the induction-todelivery interval. An outpatient approach to cervical ripening before labor induction holds promise for reducing induction costs. However, the safety and efficacy of such therapy must be subjected to scientific scrutiny. Another cost associated with labor that is induced rather than spontaneous is the more frequent request for epidural anesthesia.3,4 A possible causal association between epidural anesthesia and the increase in cesarean delivery remains to be explained. Each year in the United States, approximately 60% of women with a prior cesarean delivery undergo a trial of labor in a subsequent pregnancy. Concern persists that a trial of labor, rather than elective surgery, increases the risk of maternal complications such as a uterine rupture. Although a slightly higher rate of uterine rupture may not prohibit the practice of labor induction, it does emphasize the need for informed patient consent and for judicious observation. Studies involving the induction of labor in this circumstance are largely based on sample sizes too small to have the power to assess the risk of uterine rupture. Retrospective investigations using large
166
Rayburn and Zhang
Induction of Labor
study populations conclude that labor that is induced rather than spontaneous increases the risk of uterine rupture (from 0.7% to 2.9%) among women with one or more prior cesarean delivery.7,8 Furthermore, labor induced using prostaglandins confers a slightly greater risk (2.5–2.9%) of uterine rupture.8,9 Although the risk of uterine rupture is likely less (0.7%) with mechanical intracervical dilators such as Foley catheters, experience is too limited to offer a definitive recommendation for preinduction cervical ripening in this circumstance.9 FUTURE STUDIES FOR DEVELOPING GUIDELINES Patients need information during prenatal visits about the possibility of labor induction. When women are presented with the perceived benefits of an induction for a nonurgent indication, a balanced discussion should include the risk of additional procedures and cost. Nuutila et al10 reported that most women hold positive attitudes toward inductions when more information is given and when the patient displays concern about herself and her fetus’ health. Seeking a woman’s opinion about the method and the timing of an induction during prenatal visits may aid in her adaptation to labor. Indications for induction of labor require an awareness of the peer medical literature. Evidence-based protocols for cervical ripening and for induction of labor require acceptance by providers at each hospital. Otherwise, a specific intervention may be applied erroneously. Monitoring of induction rates also provides a clearer understanding of current community practice. Labor induction rates should be reported at hospital obstetric staff meetings. Although there may be no benchmark cutoff as to what is considered excessive, induction rates for individual physicians may require scrutiny if operative delivery rates or unfavorable perinatal outcomes are high. Several clinical techniques have been proposed to determine the precise time of onset of term labor. The presence of fetal fibronectin in cervicovaginal secretions is an indicator that may predict a successful labor induction.11 Assessing the readiness of the cervix by means of this test has the potential to obviate the need to induce labor in certain cases. For example, when the result is positive, it may be better to wait until the onset of spontaneous labor, which is expected to be within 3 days. Likewise, when a negative result is accompanied with a low Bishop score, an induction of labor should be conducted only on the basis of a valid indication.11 Most recent labor induction studies have dealt primarily with safety and efficacy issues of preinduction cervical ripening agents or regimens. Few have assessed overall trends in reported indications for induction. In attempt-
OBSTETRICS & GYNECOLOGY
ing to optimize success with induction of labor, women at greatest risk for cesarean delivery should be identified. Future investigations should consider variables known to influence the finding of a prolonged latent phase, dysfunctional labor, and arrest of dilatation. Examples of confounding variables include provider type, parity, gestational age, preinduction condition of the cervix, any cervical ripening method, and dosing regimen of oxytocin. Short of randomized clinical trials, it is difficult to precisely measure the effect of induction of labor in terms of cost, psychologic effects, and intrapartum procedures such as epidural analgesia, instrumental delivery, or cesarean delivery. For any marginal indication, a trend should be observed to support the need for such a randomized trial. This will require a multicenter approach with common methodologies to recruit a larger study population. Such larger investigations have the additional benefit of providing data on safety issues relating to the fetus as well as for the mother. REFERENCES 1. Zhang J, Yancey MK, Henderson CE. National trends in labor induction, 1989 –1998. J Reprod Med 2002;47: 120 – 4. 2. Yeast JD, Jones A, Poskin M. Induction of labor and the relationship to cesarean delivery: A review of 7001 consecutive inductions. Am J Obstet Gynecol 1999;180:628 –33. 3. Crowley P. Interventions for preventing or improving the outcome of delivery at or beyond term. Cochrane Database Syst Rev 2000;2:CD000170.
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4. Smith LP, Nagourney BA, McLean FH, Usher RH. Hazards and benefits of elective induction of labor. Am J Obstet Gynecol 1984;148:579 – 85. 5. The National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units. A clinical trial of induction of labor versus expectant management in postterm pregnancy. Am J Obstet Gynecol 1994; 170:716 –23. 6. Conway DL, Langer O. Elective delivery of infants with macrosomia in diabetic women: Reduced shoulder dystocia versus increased cesarean deliveries. Am J Obstet Gynecol 1998;178:922–5. 7. Conway DL, Adkins WB, Schroeder B, Langer O. Isolated oligohydramnios in the term pregnancy: Is it a clinical entity? J Matern Fetal Med 1998;7:197–200. 8. Lydon-Rochelle M, Holt V, Easterling T, Martin D. Risk of uterine rupture during labor among women with a prior cesarean delivery. N Engl J Med 2001;345:3– 8. 9. Ravasia DJ, Woods SL, Pollard JK. Uterine rupture during induced trial of labor among women with previous cesarean delivery. Am J Obstet Gynecol 2000;183: 1176 –9. 10. Nuutila M, Halmesmaki E, Hiilesmaa V, Ylikorkala O. Women’s anticipations of and experiences with induction of labor. Acta Obstet Gynecol Scand 1999;78:704 –9. 11. Kiss H, Ahner R, Hohlagschandtner M, Leitich H, Husslein P. Fetal fibronectin as a predictor of term labor: A literature review. Acta Obstet Gynecol Scand 2000;79: 3–7. Received December 28, 2001. Received in revised form March 1, 2002. Accepted March 14, 2002.
Rayburn and Zhang
Induction of Labor
167
Rising Rates of Labor Induction: Present Concerns and Future Strategies William F. Rayburn, MD, and Jun Zhang, MD, PhD Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, School of Medicine, University of New Mexico, Albuquerque, New Mexico; and Epidemiology Branch, National Institute of Health and Human Development, National Institutes of Health, Bethesda, Maryland
The rate of labor induction nationwide increased gradually from 9.5% to 19.4% between 1990 and 1998. Reasons for this doubling of inductions relate to widespread availability of cervical ripening agents, pressure from patients, conveniences to physicians, and litigious constraints. The increase in medically indicated inductions was slower than the overall increase, suggesting that induction for marginal or elective reasons has risen more rapidly. Data to support or refute the benefits of marginal or elective inductions are limited. Many trials of inductions for marginal indications are either nonexistent or retrospective with small sample sizes, thereby limiting definitive conclusions. Until prospective clinical trials can better validate reasons for the liberal use of labor induction, it would seem prudent to maintain a cautious approach, especially among nulliparous women. Strategies are proposed for developing evidence-based guidelines to reduce the presumed increase in health care costs, risk of cesarean delivery for nulliparas, and overscheduling in labor and delivery. (Obstet Gynecol 2002;100:164 –7. © 2002 by The American College of Obstetricians and Gynecologists.)
Induction of labor is one of the most common procedures in obstetrics. Since 1989, all states and the District of Columbia have used a new standardized certificate of live birth that contains a check box for “induction of labor.” Birth certificate data reported to the National Center for Health Statistics revealed that the rate of labor induction increased gradually from 9.5% to 19.4% for all births between 1990 and 1998.1 These rates varied widely between and within many states. For example, induction rates in 1998 ranged from 10.9% in Hawaii to 41.6% in Wisconsin and from 6.5% to 53.2% in counties of New York. Address reprint requests to: William F. Rayburn, MD, University of New Mexico Health Sciences Center, Department of Obstetrics and Gynecology, 2211 Lomas Boulevard NE (ACC 4), Albuquerque, NM 87131-5286; E-mail: [email protected].
164
Although transfer of information to the birth certificate is potentially fallible, the number of labor inductions now exceeds the combined number of primary cesarean deliveries, vaginal births after cesarean, and operative vaginal deliveries. In the United States, induction rates exceeding 40% of all births may be found at many community hospitals.2 EXPLANATIONS FOR RISING RATES Explanations for this doubling in labor inductions are complex and multifactorial. An improved ability to plan the timing of birth by the physician, patient, and her family is the most common reason. Other explanations include the presence of a very favorable cervix (Bishop score greater than 8) at term, availability of cervical ripeners, more relaxed attitudes toward marginal or elective inductions, and presumed medical liability from continued expectant management. Lastly, pressures by demanding patients or financial gain by the provider are unspoken reasons to induce labor. Indications for induction of labor are not absolute. Examples of maternal or fetal conditions that may be indications include abruptio placentae, premature rupture of membranes, post-term pregnancy, active medical conditions, fetal compromise, and preeclampsia/eclampsia. Better detection has identified pregnancies at risk. For example, borderline hypertensive disorders or an abnormally low volume of amniotic fluid are common indications for induced labor.1 Although inductions for pregnancies with abruptio placentae and multifetal pregnancy are infrequent, their rates have also increased significantly.1 White women are more likely than those of other races to have an induced labor. Maternal age has little impact, except in very young women where induced labor is less common.1 Induction rates are higher with higher formal education and with earlier prenatal care. Nulliparas have a higher induction rate than do multiparas. ELECTIVE OR MARGINAL INDICATIONS Induction of labor has undisputable merit as a therapeutic option when benefits of expeditious delivery clearly outweigh the risks of continuing a pregnancy. Although there is no universally accepted definition, an elective induction is generally accepted to be the absence of maternal or fetal indications. The number of elective inductions has risen rapidly, presumably because in-
VOL. 100, NO. 1, JULY 2002 © 2002 by The American College of Obstetricians and Gynecologists. Published by Elsevier Science Inc.
0029-7844/02/$22.00 PII S0029-7844(02)02047-1
creases of indicated inductions during the past decade were significantly lower than the overall increase (70% versus 100%).1 In some settings, elective inductions comprise up to half of all inductions and at least 10% of all births after excluding repeat cesarean deliveries.2,3 Advocates agree that elective inductions allow for better planning of daytime deliveries with theoretically a less fatigued patient and with more perinatal medical care personnel. A modest increase in instrumental delivery, in part explained by a higher rate of epidural anesthesia, has been found in most but not all studies of elective induction compared with spontaneous labor.3,4 More convincing evidence exists that elective induction at term increases the risk two-fold for a cesarean delivery among nulliparas (14 –20%).2,4 Failure to progress is the primary indication. Because induction of labor is so common, even a small additional risk of cesarean delivery for nulliparous women may translate into a larger number of cesarean deliveries nationwide. It is likely that nulliparous women differ from multiparous women in preinduction cervical effacement and dilatation and in response to ripening methods. Multiparous women generally present with a more inducible cervix. Thus, when compared with spontaneous labor, elective induction at term does not appear to pose an increased risk either to the multiparous woman or to her fetus in carefully selected populations with a very favorable cervix.3 Before the introduction of fetal surveillance techniques, prolonged pregnancy was associated with a twofold to ten-fold increase in perinatal mortality and with a two-fold to four-fold increase in the incidence of fetal distress.3 More recent studies have suggested that, despite costly monitoring techniques, the post-term fetus remains at risk for certain perinatal morbidities such as meconium aspiration, fetal intolerance to labor, and fetal macrosomia. Management of the uncomplicated pregnancy that extends 1 week beyond the estimated date of delivery is controversial. Central to this controversy is whether the fetus is at increased risk of deterioration as gestation continues. In the otherwise uncomplicated post-term pregnancy, there is little difference in perinatal outcome with expectant management compared with immediate induction. The literature does not provide a clear answer as to which management plan should be followed.5 Among pregnancies 41 weeks or longer, the cesarean delivery rate has been reported to be either increased, decreased, or unchanged among women whose labor is induced rather than spontaneous.3–5 Macrosomia, defined as a birth weight exceeding 4000 g, accounts for almost 10% of all births. Two scenarios are relatively common: macrosomia in a prior pregnancy or being suspected in the present pregnancy.
VOL. 100, NO. 1, JULY 2002
Theoretically, an induction of labor to eliminate further fetal growth should reduce the risks of cesarean delivery and of shoulder dystocia with brachial plexus injury. Decision making is complicated by inaccuracies in estimating fetal weight and by the lack of sound scientific support to justify intervention even if the fetal weight estimation is presumably accurate. Labor that is induced rather than spontaneous is associated with increased cesarean delivery rates.3 Independent studies have also reported a higher rate of induction of labor in women whose fetuses later had shoulder dystocia.3 Possible explanations for greater risks of cesarean delivery and shoulder dystocia when labor is induced include differences in labor progression, degrees of fetal head molding, strength of contractions, and more aggressive attitudes of obstetricians. Randomized trials reveal that induction of labor, compared with expectant management, does not significantly decrease the rates of shoulder dystocia and cesarean delivery in nondiabetic and diabetic populations.3–5 Furthermore, clinical trials to determine the risk of birth injury (brachial plexus injury, clavicular fractures) would require very large sample sizes.3– 6 A liberal attitude toward ordering fetal surveillance testing is common at or beyond term. Oligohydramnios (amniotic fluid index 5 or less) is often found in such pregnancies. Risks associated with oligohydramnios include meconium, umbilical cord compression, and subsequent intrapartum fetal heart rate decelerations. Oligohydramnios is considered to be isolated in the absence of hypertension, fetal anomalies, or fetal growth restriction. Induction of labor may not be warranted in cases of isolated oligohydramnios. Fetal tolerance to labor and neonatal outcome measures may not differ between groups with isolated oligohydramnios and those with a normal fluid volume. Conway et al7 reported on 183 women undergoing labor induction for isolated oligohydramnios between 37 and 416⁄7 weeks’ gestation. Compared with a control group with normal amniotic fluid measurements who presented in spontaneous labor, women who were induced had significantly more cesarean deliveries (15.8% versus 6.6%, P ⬍ .01, odds ratio 2.7). This increase of operative delivery in the oligohydramnios group was not attributable to fetal intolerance to labor. Also, fetal risk was not increased among patients who presented in spontaneous labor. Certain indications for labor induction are not validated by prior clinical investigations. Marked maternal physiologic changes of pregnancy requiring maternal treatment for edema, backache, or indigestion may explain why some inductions are undertaken at term. Some indications for induction may have no bearing on the decision to induce labor or might even be relative con-
Rayburn and Zhang
Induction of Labor
165
traindications. For example, a desired vaginal birth after cesarean delivery, a prior fetus with shoulder dystocia, or previous cephalopelvic disproportion are not documented indications for induction of labor. PRESENT CONCERNS Scheduling an induction rather than waiting for spontaneous labor offers many advantages: easing domestic arrangements, ensuring attendance of the patient’s physician, and avoiding journeys during labor either from distant places or in severe climatic conditions. Labor inductions for logistic reasons may occur so often, however, that limitations of labor and delivery resources require scheduling several days in advance. Thus, some induction attempts may be scheduled later than the clinician would desire, with many cases undergoing spontaneous labor beforehand. For the obstetrician and nursing staff, there would be value in timing deliveries during the daytime or evening on weekdays. Nursing staff hours could be staggered, so that extra nurses would be on duty at peak hours of postinduction deliveries. Although these arguments are appealing, there are insufficient published data for this practice to be recommended. Induction of labor may bear a stiff price when considering increases in costs related to maternal morbidity and cesarean delivery. Costs for the longer predelivery hospital stay among women with induced rather than spontaneous labor is noteworthy in today’s managed care environment.3 The time required for cervical ripening is important to consider when evaluating the induction-todelivery interval. An outpatient approach to cervical ripening before labor induction holds promise for reducing induction costs. However, the safety and efficacy of such therapy must be subjected to scientific scrutiny. Another cost associated with labor that is induced rather than spontaneous is the more frequent request for epidural anesthesia.3,4 A possible causal association between epidural anesthesia and the increase in cesarean delivery remains to be explained. Each year in the United States, approximately 60% of women with a prior cesarean delivery undergo a trial of labor in a subsequent pregnancy. Concern persists that a trial of labor, rather than elective surgery, increases the risk of maternal complications such as a uterine rupture. Although a slightly higher rate of uterine rupture may not prohibit the practice of labor induction, it does emphasize the need for informed patient consent and for judicious observation. Studies involving the induction of labor in this circumstance are largely based on sample sizes too small to have the power to assess the risk of uterine rupture. Retrospective investigations using large
166
Rayburn and Zhang
Induction of Labor
study populations conclude that labor that is induced rather than spontaneous increases the risk of uterine rupture (from 0.7% to 2.9%) among women with one or more prior cesarean delivery.7,8 Furthermore, labor induced using prostaglandins confers a slightly greater risk (2.5–2.9%) of uterine rupture.8,9 Although the risk of uterine rupture is likely less (0.7%) with mechanical intracervical dilators such as Foley catheters, experience is too limited to offer a definitive recommendation for preinduction cervical ripening in this circumstance.9 FUTURE STUDIES FOR DEVELOPING GUIDELINES Patients need information during prenatal visits about the possibility of labor induction. When women are presented with the perceived benefits of an induction for a nonurgent indication, a balanced discussion should include the risk of additional procedures and cost. Nuutila et al10 reported that most women hold positive attitudes toward inductions when more information is given and when the patient displays concern about herself and her fetus’ health. Seeking a woman’s opinion about the method and the timing of an induction during prenatal visits may aid in her adaptation to labor. Indications for induction of labor require an awareness of the peer medical literature. Evidence-based protocols for cervical ripening and for induction of labor require acceptance by providers at each hospital. Otherwise, a specific intervention may be applied erroneously. Monitoring of induction rates also provides a clearer understanding of current community practice. Labor induction rates should be reported at hospital obstetric staff meetings. Although there may be no benchmark cutoff as to what is considered excessive, induction rates for individual physicians may require scrutiny if operative delivery rates or unfavorable perinatal outcomes are high. Several clinical techniques have been proposed to determine the precise time of onset of term labor. The presence of fetal fibronectin in cervicovaginal secretions is an indicator that may predict a successful labor induction.11 Assessing the readiness of the cervix by means of this test has the potential to obviate the need to induce labor in certain cases. For example, when the result is positive, it may be better to wait until the onset of spontaneous labor, which is expected to be within 3 days. Likewise, when a negative result is accompanied with a low Bishop score, an induction of labor should be conducted only on the basis of a valid indication.11 Most recent labor induction studies have dealt primarily with safety and efficacy issues of preinduction cervical ripening agents or regimens. Few have assessed overall trends in reported indications for induction. In attempt-
OBSTETRICS & GYNECOLOGY
ing to optimize success with induction of labor, women at greatest risk for cesarean delivery should be identified. Future investigations should consider variables known to influence the finding of a prolonged latent phase, dysfunctional labor, and arrest of dilatation. Examples of confounding variables include provider type, parity, gestational age, preinduction condition of the cervix, any cervical ripening method, and dosing regimen of oxytocin. Short of randomized clinical trials, it is difficult to precisely measure the effect of induction of labor in terms of cost, psychologic effects, and intrapartum procedures such as epidural analgesia, instrumental delivery, or cesarean delivery. For any marginal indication, a trend should be observed to support the need for such a randomized trial. This will require a multicenter approach with common methodologies to recruit a larger study population. Such larger investigations have the additional benefit of providing data on safety issues relating to the fetus as well as for the mother. REFERENCES 1. Zhang J, Yancey MK, Henderson CE. National trends in labor induction, 1989 –1998. J Reprod Med 2002;47: 120 – 4. 2. Yeast JD, Jones A, Poskin M. Induction of labor and the relationship to cesarean delivery: A review of 7001 consecutive inductions. Am J Obstet Gynecol 1999;180:628 –33. 3. Crowley P. Interventions for preventing or improving the outcome of delivery at or beyond term. Cochrane Database Syst Rev 2000;2:CD000170.
VOL. 100, NO. 1, JULY 2002
4. Smith LP, Nagourney BA, McLean FH, Usher RH. Hazards and benefits of elective induction of labor. Am J Obstet Gynecol 1984;148:579 – 85. 5. The National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units. A clinical trial of induction of labor versus expectant management in postterm pregnancy. Am J Obstet Gynecol 1994; 170:716 –23. 6. Conway DL, Langer O. Elective delivery of infants with macrosomia in diabetic women: Reduced shoulder dystocia versus increased cesarean deliveries. Am J Obstet Gynecol 1998;178:922–5. 7. Conway DL, Adkins WB, Schroeder B, Langer O. Isolated oligohydramnios in the term pregnancy: Is it a clinical entity? J Matern Fetal Med 1998;7:197–200. 8. Lydon-Rochelle M, Holt V, Easterling T, Martin D. Risk of uterine rupture during labor among women with a prior cesarean delivery. N Engl J Med 2001;345:3– 8. 9. Ravasia DJ, Woods SL, Pollard JK. Uterine rupture during induced trial of labor among women with previous cesarean delivery. Am J Obstet Gynecol 2000;183: 1176 –9. 10. Nuutila M, Halmesmaki E, Hiilesmaa V, Ylikorkala O. Women’s anticipations of and experiences with induction of labor. Acta Obstet Gynecol Scand 1999;78:704 –9. 11. Kiss H, Ahner R, Hohlagschandtner M, Leitich H, Husslein P. Fetal fibronectin as a predictor of term labor: A literature review. Acta Obstet Gynecol Scand 2000;79: 3–7. Received December 28, 2001. Received in revised form March 1, 2002. Accepted March 14, 2002.
Rayburn and Zhang
Induction of Labor
167