Original Article
Induction of Labor as Compared with Serial Antenatal Monitoring in Post-Term Pregnancy — A Randomized Controlled Trial
N Engl J Med 1992; 326:1587-1592June 11, 1992
- Abstract
- Abstract
Background
The rates of perinatal mortality and neonatal morbidity are higher for post-term pregnancies than for term pregnancies. It is not known, however, whether the induction of labor results in better outcomes than does serial fetal monitoring while awaiting spontaneous labor.
Methods
We studied 3407 women with uncomplicated pregnancies of 41 or more weeks' duration. The women were randomly assigned to undergo induction of labor or to have serial antenatal monitoring and spontaneous labor unless there was evidence of fetal or maternal compromise, in which case labor was induced or cesarean section was performed. In the induction group, labor was induced by the intracervical application of prostaglandin E2. Serial antenatal monitoring consisted of counts of fetal kicks, nonstress tests, and assessments of amniotic-fluid volume. The outcomes we measured were the rates of perinatal mortality, neonatal morbidity, and delivery by cesarean section.
Results
Among the 1701 women in the induction group, 360 (21.2 percent) underwent cesarean section, as compared with 418 (24.5 percent) of the 1706 women in the monitoring group (P = 0.03). This difference resulted from a lower rate of cesarean section performed because of fetal distress among the women in the induction group (5.7 percent vs. 8.3 percent, P = 0.003). When two infants with lethal congenital anomalies were excluded, there were no perinatal deaths in the induction group and two stillbirths in the monitoring group (P not significant). The frequency of neonatal morbidity was similar in the two groups.
Conclusions
In post-term pregnancy, the induction of labor results in a lower rate of cesarean section than serial antenatal monitoring; the rates of perinatal mortality and neonatal morbidity are similar with the two approaches to management. (N Engl J Med 1992;326:1587–92.)
Media in This Article
Table 1
Base-Line Characteristics of the Women in the Induction, Monitoring, and Data-Only Groups.*Table 2
Reasons for the Induction of Labor, According to Study Group.*Article Activity
- Article
APPROXIMATELY 10 percent of all pregnancies last longer than 41 to 42 weeks,1 , 2 and the risk of perinatal death increases in pregnancies that last 2 or more weeks beyond the due date.2 3 4 Much of this perinatal mortality is related to asphyxia with or without meconium in the amniotic fluid.4
During the past 30 to 40 years, post-term pregnancies have been managed in two ways. The first approach is to induce labor when the pregnancy reaches 41 to 42 weeks' gestation.5 This approach has been most popular when the cervix is already dilated. The other approach is to institute monitoring with serial tests of fetal well-being, await spontaneous labor, and induce labor only if there is evidence of fetal or maternal compromise.6 7 8 It is unclear which is the better approach for the management of post-term pregnancy.9
The Canadian Multicenter Post-term Pregnancy Trial was undertaken to determine what effects a policy of inducing labor at 41 or more weeks' gestation would have on perinatal mortality and neonatal morbidity as compared with a policy of expectant management with serial antenatal monitoring. A secondary objective of the trial was to determine whether induction of labor would result in a higher or lower rate of cesarean section. This trial was a management study, designed to be carried out under usual rather than ideal clinical conditions.
Methods,
The trial was approved by the research ethics committees at all the participating centers, and the women gave informed consent before enrollment in the study.
The trial was conducted in 22 hospitals throughout Canada between November 1985 and December 1990. Randomization was centrally controlled at McMaster University. To ensure the comparability of the two groups, the groups were stratified in blocks of four and eight subjects according to center, parity, and duration of gestation at the time of randomization.
Eligibility Criteria
Pregnant women were considered eligible for the study if their pregnancies had reached 41 or more weeks' gestation (287 or more days) and if they had a live singleton fetus. Gestational age was determined by one of the following methods: according to the date of the last menstrual period preceded by regular cycles without use of oral contraceptives or the known date of conception, confirmed by a pregnancy test at <6 weeks, a physical examination at ≤20 weeks, or ultrasonography at ≤26 weeks; by ultrasonography at ≤26 weeks if the date of the last menstrual period was uncertain; or by ultrasonography on two occasions at ≤26 weeks that resulted in consistent estimates of gestational age, if the date of the last menstrual period was unknown.
Women were excluded from the study if the cervix was dilated ≥3 cm, if the gestational age was ≥44 weeks, if the presentation of the fetus was noncephalic, or if there was evidence of a lethal congenital anomaly, maternal diabetes mellitus, preeclampsia, intrauterine growth retardation, or prelabor rupture of membranes. Women were also excluded if there was a need for urgent delivery (e.g., in cases of fetal distress or antepartum bleeding) or if vaginal delivery was contraindicated (e.g., in cases of placenta previa). Other reasons for exclusion were a previous cesarean section and addiction to drugs or alcohol.
Study Protocol
The women were enrolled as outpatients. Among those assigned to the induction group, labor was to be induced within four days after randomization. If the cervix was less than 3 cm dilated and less than 50 percent effaced and the fetal heart rate was normal, the woman was given prostaglandin E2 gel (Prepidil; 0.5 mg intracervically) to "ripen" the cervix or induce labor. After the insertion of the gel, the fetus was monitored continuously for a minimum of one hour. A maximum of three doses of the gel could be given at intervals of six hours. If the gel was not used or if it did not induce labor, labor was induced by the intravenous administration of oxytocin, amniotomy, or both. The oxytocin infusion was not started until 12 hours after the last insertion of the gel.
Women assigned to the monitoring group were asked to count the number of times they felt the fetus kick over a two-hour period each day (kick counts) and underwent nonstress tests three times per week; ultrasonographic assessment of amniotic-fluid volume was performed two to three times per week. The fetal monitoring was usually carried out in the fetal-assessment units of the participating centers by obstetricians or radiologists. The women were asked to contact their physicians if they counted fewer than six kicks in 2 hours and to have a nonstress test within 12 hours. If the nonstress test was nonreactive or showed decelerations in the heart rate, if the amniotic-fluid volume was low (a pocket of <3 cm), if obstetrical complications developed, or if the gestational age reached 44 weeks, the fetus was to be delivered immediately, either by inducing labor by means of amniotomy or the intravenous administration of oxytocin or by cesarean section. In all cases, the fetal heart rate was electronically monitored continuously during labor.
The mode of delivery was determined by the attending physician. At delivery, cord-blood gases (venous and arterial) and the cord-blood hematocrit were measured, and Apgar scores were determined by independent observers. If the Apgar score was less than 7 at 5 minutes, it was determined again at 10 minutes. The infants were assessed by the physicians chosen by the parents; these physicians were aware of the method of managing labor. At each center the study coordinators collected data on outcomes from the hospital charts, usually after the discharge of the mother and baby.
Outcomes
The primary outcomes assessed in this study were perinatal mortality and neonatal morbidity. Perinatal mortality was defined before the trial as stillbirth or neonatal death before discharge (excluding deaths caused by lethal congenital anomalies). Neonatal morbidity was defined as an Apgar score less than 7 at 5 minutes, asphyxial encephalopathy (seizures, alterations in levels of consciousness or tone, or a need for tube feeding, during the first 48 hours of life), or respiratory distress (oxygen requirement >40 percent and respiratory rate >60 breaths per minute, both within 12 hours after birth and persisting for more than 24 hours, or assisted ventilation for more than 24 hours). Infants with lethal congenital anomalies and stillborn infants were excluded from calculations of neonatal morbidity. The secondary outcome assessed in this study was delivery by cesarean section.
Sample Size
The required sample size was estimated to be 3400. This figure was based on a power of 80 percent of finding a reduction of 50 percent or more in the incidence of an Apgar score less than 7 at five minutes. We estimated that this sample size would provide a power of 95 percent of finding a reduction of 25 percent or more in the rate of cesarean section.
Redefinition of Neonatal Morbidity
During the trial, the definition of asphyxial encephalopathy was changed to omit alterations in levels of consciousness or tone or need for tube feeding during the first 48 hours of life and to add the presence of neurologic abnormalities after 5 days of age or at discharge, whichever was sooner.
An adjudication of all potentially abnormal neonatal outcomes among the first 1500 infants born in the course of the study was undertaken by a neonatologist who was unaware of the mothers' group assignments. Because there were some areas of disagreement between the results of the neonatal adjudication and the changed definitions of neonatal morbidity, a consensus conference was held to define further the measures of neonatal morbidity in post-term infants and to develop an index of perinatal mortality and neonatal morbidity. The details of this process will be reported separately. The panelists were not privy to information from the trial. The measures of neonatal morbidity identified by the panelists were the Apgar scores at 1 minute, 5 minutes, and 10 minutes; the birth weight; the need for resuscitation; the base deficit; the presence of meconium in the amniotic fluid; hypotonia; the infant's level of consciousness; the need for tube feeding; seizures; hypoglycemia; hyperbilirubinemia; trauma; respiratory distress; and the length of stay in a neonatal intensive care unit (details of these measures are described elsewhere*). Each measure was broken down into levels of severity and given a weight. After all infants with major congenital anomalies were excluded, each infant accumulated points for mortality and for each level of morbidity. Thus, a lower score on this index indicated a better outcome. For babies who survived, the range of the index was 0 to 4900 (maximal possible score, 10,160). The index was revised to adapt to the data collected by excluding hyperbilirubinemia and making other minor changes.
Before undertaking the analysis, we carried out a power calculation based on various cutoff points for the index. If the overall incidence of perinatal mortality and neonatal morbidity (defined as a score at or above the cutoff point on this index) in our population were 2 percent, then with our sample size we would have an 80 percent chance of detecting a statistically significant difference if this score were reduced by 50 percent in one of the study groups. In our sample, 2 percent of all babies had an index score ≥586. Consequently, we used 586 as our cutoff in transforming the index score into a binary outcome variable (<586 vs. ≥586).
Statistical Analysis
The results were analyzed according to intention to treat, and all women who underwent randomization for whom outcome data were available were included in the analysis. Major congenital anomalies were identified by investigators who were unaware of the mother's study group, and infants with such anomalies were excluded from the analysis of perinatal mortality and neonatal morbidity. Stillborn infants were excluded from the analysis of individual measures of neonatal morbidity. Two interim analyses were undertaken, after the enrollment of 500 and 1500 women.
The groups were compared by means of contingency-table chi-square analyses for categorical and binary variables and by chi-square analysis for linear trend for ordered categorical variables. The index of perinatal mortality and neonatal morbidity was analyzed in three ways: as a raw score; with the infants divided into six ordered index-score categories at the cutoff points 1, 586, 1000, 1500, and 2000; and as a binary outcome variable (<586 vs. ≥586). The groups were compared with respect to the raw score by means of the Wilcoxon rank-sum test, with respect to the ordered categorical variables by means of chi-square analysis for linear trend, and with respect to the binary outcome variables by means of a contingency-table chi-square analysis. In addition, we compared the study groups with respect to the binary index-score variable and the mode of delivery (cesarean or vaginal), while controlling for other factors, by means of multiple logistic regression. The Breslow—Day test for homogeneity of odds ratios was used to test for any interaction between the treatment group and study center.Two-sided P values are reported for all significance tests; a P value of <0.05 was considered to indicate statistical significance.
*See NAPS document no. 04948 for six pages of supplementary material. Order from NAPS c/o Microfiche Publications, P.O. Box 3513, Grand Central Station, New York, NY 10163–3513. Remit in advance (in U.S. funds only) $7.75 for photocopies or $5 for microfiche. Outside the U.S. and Canada add postage of $4.50 ($1.75 for microfiche postage). There is a $15 invoicing charge on all orders filled before payment.
Results
During the study period 6354 women were considered eligible for the study; 3418 (54 percent) were enrolled. Of the remaining women, 1955 (31 percent of the original group) agreed to provide us with base-line data (data-only group).
Of the women enrolled in the study, no data were received for 11. The analysis of the base-line characteristics and maternal outcomes therefore included 3407 women, of whom 1701 were assigned to the induction group and 1706 to the monitoring group (Table 1Table 1
Base-Line Characteristics of the Women in the Induction, Monitoring, and Data-Only Groups.*). After randomization, an additional seven women whose infants had major congenital anomalies were excluded from the analysis of perinatal and neonatal outcomes. Two of these babies had transposition of the great vessels, one had an inborn error of metabolism, one had a large cystic hygroma, one had hydrocephalus, one had a diaphragmatic hernia, and one had hypoplastic left-heart syndrome; the last two died during the perinatal period.Management of Pregnancy
There was compliance with the monitoring protocol in the cases of 88 percent of the women in this group. Labor was more often induced in the induction group (1124 women [66.1 percent]) than in the monitoring group (554 women [32.5 percent], P<0.001). The women in the induction group were less likely not to have delivered their babies seven or more days after randomization (86 [5.1 percent] vs. 443 [26.0 percent], P<0.001). The reasons for induction of labor and the methods of induction in the two groups are shown in Tables 2Table 2
Reasons for the Induction of Labor, According to Study Group.* and 3Table 3
Method of Inducing Labor, According to Study Group.*.Cesarean Section and Maternal Outcomes
The rate of cesarean section was significantly higher among women in the monitoring group than among those in the induction group (418 [24.5 percent] vs. 360 [21.2 percent], P = 0.03), after we controlled for parity, maternal age, cervical dilatation at the time of randomization, and race. The odds ratio was 1.22 (95 percent confidence interval, 1.02 to 1.45 for the monitoring group as compared with the induction group). The result of the test for an interaction of study group by center was not significant (P = 0.21). In addition to the study group, variables that had a significant independent effect on whether a woman would undergo a cesarean section were parity (0 vs. ≥1; odds ratio, 7.06; P<0.001), maternal age (measured in decades; odds ratio, 1.53; P<0.001), cervical dilatation at the time of randomization (0 cm, 1 to 2 cm, or 3 to 4 cm; odds ratio, 1.40; P<0.001), and race (white, black, Asian, or other; P = 0.0044). Specifically, there was a higher likelihood of cesarean section among nulliparous women, older women, women in whom the cervix was less fully dilated at the time of randomization, black women, and women in the "other" racial category. There was no significant interaction between the study group and any of these factors.
There was a significantly lower rate of cesarean section performed because of fetal distress among women in the induction group than among those in the monitoring group (97 [5.7 percent] vs. 141 [8.3 percent], P = 0.003). There was no difference in the rate of cesarean section performed because of dystocia (failure of labor to progress, failure of induction of labor, or incoordinate uterine action) between the two groups.
For women who delivered vaginally, there was a similar rate of instrumental delivery in the induction group (473 of 1341 [35.3 percent]) and the monitoring group (449 of 1288 [34.9 percent]). The rate of use of analgesia or anesthesia was similar in the induction group (1558 [91.6 percent]) and the monitoring group (1551 [91.0 percent]).
Table 4 shows the distribution and type of antepartum and intrapartum complications in the two groups. The frequency of fetal distress was lower in the induction group than in the monitoring group (10.3 percent vs. 12.8 percent, P = 0.017), and there was a lower incidence of meconium staining of the amniotic fluid in the induction group (25.0 percent vs. 28.7 percent, P = 0.009). There was no difference in the type of meconium staining (thick vs. thin) between the two groups, nor were there any significant differences in the frequency of cord prolapse, abruptio placentae, uterine hypertonus, rupture of membranes more than 24 hours before delivery, or shoulder dystocia. The frequency of postpartum maternal morbidity (hemorrhage, sepsis, or endometritis) did not differ between the two groups (data not shown).
Perinatal Mortality and Neonatal Morbidity
There were two stillbirths in the monitoring group and none in the induction group. In the case of the first stillbirth, a 28-year-old woman with two previous live-born children began fetal-movement counts on the day of randomization. Three days later the intrauterine death of the fetus was confirmed. Meconium staining of the membranes was noted at delivery. The stillborn infant weighed 3175 g at delivery. An autopsy revealed hypoxic—ischemic encephalopathy. In the second case, a 31-year-old woman in her first pregnancy had normal results on a nonstress test and a normal amniotic-fluid—volume assessment on the day of randomization; antenatal testing continued until labor began spontaneously five days later. Acute fetal distress was diagnosed, and an emergency cesarean section was performed. The stillborn infant, who could not be resuscitated, weighed 2600 g. The autopsy revealed massive aspiration of meconium.
There were no neonatal deaths in either group. The two groups did not differ significantly in the rate of perinatal mortality and neonatal morbidity either when we analyzed the results for infants with index scores ≥586 as compared with those with scores <586 or when we divided the index scores into ordered categories and analyzed them with the test for linear trend (Table 5Table 5
Perinatal Mortality and Neonatal Morbidity According to Study Group.*). Analysis of the index score with use of the Wilcoxon rank-sum test showed a significantly greater probability of a lower score (better outcome) in the induction group than in the monitoring group. This difference was due to differences between the groups at the lowest scores and is probably of no clinical importance. There was a higher risk of an index score ≥586 among infants born to nulliparous women (odds ratio, 3.48; P = 0.001), and a trend toward a higher risk among infants born to women in the group with low socioeconomic status (odds ratio, 1.16; P = 0.0629). Individual measures of neonatal morbidity did not differ between the groups (Table 6Table 6
Individual Measures of Neonatal Morbidity According to Study Group.*).There was no significant difference between the groups in terms of perinatal mortality and neonatal morbidity whether the data were analyzed with use of the original definitions of these outcomes (62 of 1700 [3.6 percent] vs. 55 of 1705 [3.2 percent]) or with use of the revised definitions (27 of 1700 [1.6 percent] vs. 30 of 1705 [1.8 percent]).
Discussion
In this study, a policy of inducing labor at 41 or more weeks of gestation was not associated with any difference in the risk of perinatal mortality and neonatal morbidity as compared with serial antenatal monitoring. There were two stillbirths in the monitoring group and no deaths in the induction group, a difference that may have been due to chance. The overall perinatal mortality rate in the trial (0.6 per 1000) was substantially lower than the rates frequently quoted (2.2 to 2.4 per 1000).11 To detect a reduction of 50 percent in the risk of perinatal mortality resulting from a policy of induction of labor in post-term pregnancy, a trial enrolling approximately 30,000 women would be required. In the absence of such a trial, one must rely on cumulative data, such as those from the Oxford Database of Perinatal Trials9 that were summarized in a review of the effects on perinatal death of the policy of inducing labor in post-term pregnancy. When our data were combined with those reported by Crowley,9 there were seven deaths with expectant management (two in our trial and five in previous trials) and only one death with induction of labor. If anything, therefore, a policy of inducing labor in post-term pregnancy may decrease the perinatal mortality rate.
We found a lower rate of cesarean section among the women in the induction group than among those in the monitoring group because of a lower rate of cesarean section for fetal distress. Because our trial did not use blinding, the differences in the rates of cesarean section may have been due to differences in the interpretation of fetal heart-rate tracings. A physician may be more likely to perform a cesarean section at 43 weeks of gestation than at 41 weeks, or when labor has been induced. The higher incidence of meconium staining in the monitoring group may also have contributed to the higher rate of cesarean section in this group.
It may be argued that the lack of use of prostaglandin E2 gel for cervical ripening in the monitoring group accounted for the difference in the rate of cesarean section. We used intracervical prostaglandin E2 for cervical ripening in the induction group since we believed that the evidence favored its use when induction was to be undertaken in women in whom the cervix was not yet dilated.12 There was insufficient evidence, in our view, to justify its use in the presence of fetal compromise. Indeed, the fetal heart rate had to be normal before the gel was inserted in women in the induction group. We elected not to allow the use of the gel in the monitoring group because we thought that most of the women in that group who would require induction of labor would have evidence of fetal compromise (abnormal nonstress-test results or decreased amniotic-fluid volume). One can only speculate about what the results would have been if prostaglandin gel had been used for women in the monitoring group or for all women who had evidence of fetal compromise.
Because most cesarean sections were performed to safeguard the welfare of the fetus, it is possible that the increased rate of cesarean section among the women in the monitoring group resulted in a lower rate of perinatal mortality and neonatal morbidity than might otherwise have occurred.
Ten randomized controlled trials listed in the Oxford Database of Perinatal Trials have evaluated the effectiveness of the induction of labor in post-term pregnancy.13 14 15 16 17 18 19 20 21 22 The results of the overview of these trials are consistent with our findings.9 We conclude that inducing labor in women with post-term pregnancies results in a decrease in the rate of cesarean section as compared with serial antenatal monitoring and no difference in the incidence of perinatal mortality and neonatal morbidity.
Supported by a grant (MA-8472) from the Medical Research Council of Canada.
*The participants in the Canadian Multicenter Post-term Pregnancy Trial Group are listed in the Appendix.
We are indebted to Dr. Iain Chalmers, Dr. David Sackett, and Dr. Colm O'Herlihy for their presentations at meetings of the investigators of the Trial Group; to the Department of Obstetrics and Gynecology of the University of Toronto for supporting the initial workshop in December 1984; and to the Upjohn Company of Canada for supplying the prostaglandin E2 gel.
Source Information
From the Department of Obstetrics and Gynecology, Women's College Hospital, University of Toronto, Toronto (M.E.H., W.J.H.); the Department of Pediatrics, Hospital for Sick Children, University of Toronto, Toronto (J.H.); and the Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ont. (M.E.H., S.H., R.M., A.W.). Address reprint requests to Dr. M.E. Hannah at Women's College Hospital, 76 Grenville St., Toronto, ON M5S 1B2, Canada.
Appendix
The participants in the Canadian Multicenter Post-term Pregnancy Trial Group were as follows: Hospital Investigators and Coordinators: E. Luther, D. Young, K. Phalen-Kelly, P. Zimmer, and H. Piccinini (Grace Maternity Hospital, Halifax, N.S.); J.-M. Moutquin, D. Parent, H. Laliberté, and F. Cloutier (Hôpital St. François d'Assise, Quebec, Que.); J.-P. Verreault, G. Paradis, and M.-T. Trudel (Hôpital St. Sacrement, Quebec, Que.); R. Gauthier and M. Corriveau (Hôpital Ste. Justine, Montreal); J.-M. Moutquin, G. Amyôt, and C. Rainville (Hôpital Nôtre-Dame, Montreal); N. Demianczuk (Ottawa General Hospital, Ottawa, Ont.); B. Thomas, B. Fallis, J. Weston, and C. Landy (Women's College Hospital, Toronto); K. Ritchie and C. Pierce (Mount Sinai Hospital, Toronto); D. Gare, H. Taylor, and J. Ingall (Toronto General Hospital, Toronto); D. Steele, L. Plauntz, and J. Hall (Wellesley Hospital, Toronto); K. Tessler and E. Heikoop (St. Michael's Hospital, Toronto); D. Xuereb, J. Weston, E. Anderson, and J. Wilson (North York General Hospital, North York, Ont.); D. Lamont, S. Burlock, and J. Gardner (St. Joseph's Hospital, Hamilton, Ont.); K. Lamont, S. Langthorne, V. Adam, and H. Campeau (Henderson Hospital, Hamilton, Ont.); P. Mohide, V. Hunter, and R. Stanhope (McMaster University Medical Centre, Hamilton, Ont.); R. Natale, D. Sharpe, and C. Nasello-Paterson (St. Joseph's Hospital, London, Ont.); L. Hanson, S. Ceslak, and D. Barber (University Hospital and St. Paul's Hospital, Saskatoon, Sask.); P. Woodrow, R. Turnell, A. Joshi, and J. Prescot (Regina General Hospital, Regina, Sask.); F. Morcos and L. Gillespie (Misericordia Hospital, Edmonton, Alta.); D. Farquharson, J. Walker, P. Brewis, M. Lee, H. Penn, D. Pottinger, and L. Palmer (Grace Hospital, Vancouver, B.C.); H. Streeter, G. Hallam, and K. Stafford (Victoria General Hospital, Victoria, B.C.); Advisory Committee: M. Bracken (Yale University, New Haven, Conn.), B. Haynes (McMaster University, Hamilton, Ont.), and A. Grant (National Perinatal Epidemiology Unit, Oxford, England); Neonatal-Outcomes Adjudicator: J. Sinclair (McMaster University, Hamilton, Ont.).
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Barbara Kiesewetter, Rainer Lehner. (2012) Maternal outcome monitoring: induction of labor versus spontaneous onset of labor—a retrospective data analysis. Archives of Gynecology and Obstetrics
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Jane E. Norman. 2012. Induction and Augmentation of Labour. , 287-295.
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Aaron B. Caughey. 2012. Post-Term Pregnancy. , 269-286.
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M.-V. Sénat. (2011) Place de l’évaluation de la quantité de liquide amniotique, du score biophysique et du doppler dans la surveillance des grossesses prolongées. Journal de Gynécologie Obstétrique et Biologie de la Reproduction
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J.-B. Haumonté, C. d’Ercole. (2011) Grossesses prolongées (termes dépassés) : à partir de quand doit-on surveiller et à quelle fréquence ?. Journal de Gynécologie Obstétrique et Biologie de la Reproduction
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L. Sentilhes, P.-E. Bouet, M. Mezzadri, V. Combaud, S. Madzou, F. Biquard, P. Gillard, P. Descamps. (2011) Évaluation de la balance bénéfice/risque selon l’âge gestationnel pour induire la naissance en cas de grossesse prolongée. Journal de Gynécologie Obstétrique et Biologie de la Reproduction
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MALIN THORSELL, SVEN LYRENÄS, ELLIKA ANDOLF, MAGNUS KAIJSER. (2011) Induction of labor and the risk for emergency cesarean section in nulliparous and multiparous women. Acta Obstetricia et Gynecologica Scandinavica 90:10, 1094-1099
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Paul D. Simpson, Katharine P. Stanley. (2011) Prolonged pregnancy. Obstetrics, Gynaecology & Reproductive Medicine 21:9, 257-262
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TINE GREVE, SØREN LUNDBYE-CHRISTENSEN, CARSTEN N. NICKELSEN, NIELS J. SECHER. (2011) Maternal and perinatal complications by day of gestation after spontaneous labor at 40-42 weeks of gestation. Acta Obstetricia et Gynecologica Scandinavica 90:8, 852-856
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OLE BREDAHL RASMUSSEN, STEEN RASMUSSEN. (2011) Cesarean section after induction of labor compared with expectant management: no added risk from gestational week 39. Acta Obstetricia et Gynecologica Scandinavica 90:8, 857-862
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Dan Selo-Ojeme, Cathy Rogers, Ashok Mohanty, Naseem Zaidi, Rose Villar, Panicos Shangaris. (2011) Is induced labour in the nullipara associated with more maternal and perinatal morbidity?. Archives of Gynecology and Obstetrics 284:2, 337-341
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Ingegerd HILDINGSSON, Annika KARLSTRÖM, Astrid NYSTEDT. (2011) Women’s experiences of induction of labour - Findings from a Swedish regional study. Australian and New Zealand Journal of Obstetrics and Gynaecology 51:2, 151-157
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Sarah Osmundson, Robin J. Ou-Yang, William A. Grobman. (2011) Elective Induction Compared With Expectant Management in Nulliparous Women With an Unfavorable Cervix. Obstetrics & Gynecology 117:3, 583-587
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Anjali J. Kaimal, Sarah E. Little, Anthony O. Odibo, David M. Stamilio, William A. Grobman, Elisa F. Long, Douglas K. Owens, Aaron B. Caughey. (2011) Cost-effectiveness of elective induction of labor at 41 weeks in nulliparous women. American Journal of Obstetrics and Gynecology 204:2, 137.e1-137.e9
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Arwa Abbas Hussain, Mohammad Yawar Yakoob, Aamer Imdad, Zulfiqar A Bhutta. (2011) Elective induction for pregnancies at or beyond 41 weeks of gestation and its impact on stillbirths: a systematic review with meta-analysis. BMC Public Health 11:Suppl 3, S5
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