elective induction of labor: a prospective clinical study

Vierhout et al., Elective induction of labor: I 155

Original articles

J. Perinat. Med.13(1985) 155

Elective induction of labor: a prospective clinical study,!: Obstetricand neonatal effects

M. E. Vierhout, J. J. Out*, H. C. S. Wallenburg

Departments of Obstetrics and Gynecology, and Medical Psychology*,Erasmus University Medical School, Rotterdam, the Netherlands

1 Introduction

Elective induction of labor should be defined asinduction of labor in the absence of a medical-obstetric indication for termination of pregnan-cy. There is considerable disagreement with re-gard to the advantages and disadvantages ofthis obstetric procedure [2, 4, 8, 9, 17, 20, 22].Those who are in favor emphasize the safetyof the procedure [10] because labor can bescheduled during the daytime when it is assu-med that optimal care can be given [10, 16].Fetal monitoring can be used from the begin-ning of labor. The potential to prevent termfetal death of unknown cause has also been putforward as an argument in favor of electiveinduction of labor [1, 11].Reported disadvantages include the feeling thatit is an unnatural procedure [2], the danger ofan induced premature delivery [7], the risks ofoverstimulation of uterine activity by oxytocin[13], prolaps of the umbilical cord and intraute-rine infection caused by artificial rupture ofmembranes [21], and the discomfort of immobi-lization for the patient [15].A critical assessment of such potential advanta-ges and disadvantages appears to be hardlypossible on the basis of the available literaturebecause of the use of different and often ill-defined definitions of elective induction. Fur-thermore, in the majority of these retrospectivestudies, criteria for selection of patient groups

Curriculum vitae

MARK E. VIERHOUT wasborn in 1948 in Djakarta(Indonesia). He studiedmedicine at the Universityof Groningen. From 1976to 1978 he worked in theSt. Elisabeth Hospital inCuracao, Dutch Antilles.From 1978 to 1983 he didhis residency in Obstetricsand Gynecology at the Uni-versity Hospital Dijkzigt,Rotterdam. In 1983 he received a Ph. D.from the ErasmusUniversity, Rotterdam with a thesis on elective inductionof labor. At present he is employed as an obstetrician andgynecologist at the Medical Department of Brunei ShellPetroleum Company Ltd. in Brunei, N. W. Borneo.

are not presented. Such criteria are only givenin one prospective study in which the results of43 elective inductions are discussed [19].The present prospective study was performedto determine the differences between electiveinduction and spontaneous labor with regardto obstetric and neonatal outcome, as well asto development of the infants in the first year.

2 Patients and methods

All women who took part in this study weredelivered in the Department of Obstetrics, Uni-

© 1985 by Walter de Gruyter Co. Berlin · New York

156 Vierhout et al., Elective induction of labor: I

versity Hospital — Dijkzigt, Rotterdam, be-tween May 1980 and September 1981. Womenin whom labor was electively induced constitutethe "induction group". The obstetric and neo-natal outcome in this group was compared tothe outcome in a reference group of women inwhom labor started spontaneously and whowere selected in the same period of time.

2.1 Criteria for selection

The study group was selected from healthywomen receiving antenatal care in our clinicstarting in the first trimester. Gestational agewas substantiated by ultrasound examination

, between 18 and 20 weeks' amenorrhea and onlysingleton pregnancies were included. Womenwith a complicated obstetric history or withcomplications in the present pregnancy wereexcluded (Tab. I). Women who met the criteriato take part in the study at 36 weeks' gestationalage and who had a fetus with a cephalic presen-tation without cephalopelvic dysproportion we-re given written and oral information about theprocedure of elective induction of labor. Theywere at all times allowed a free choice of electiveinduction or spontaneous labor. A set of "mat-ched controls" was used as a reference group.Each woman who was electively induced wasmatched with a healthy woman with an uncom-

plicated pregnancy who went into spontaneouslabor. Three criteria were used for matching:age (< 22, 23 — 27, > 28 years), parity (nullipa-rous or parous) and cultural nationality (Dutchor non-Dutch). The reference group was alsoselected around the 36th week of pregnancy.There were 28 women in the reference group inwhom complications occurred between the 36thweek and delivery. For this reason the inductiongroup consists of 184 women as compared with156 women in the reference group.

2.2 The induction group

In women who opted for elective induction oflabor, cervical ripeness was assessed in the 38thweek of pregnancy with the use of the BURN-HILL score [3]. When the cervix was considered"ripe" — a score greater than four — the datefor induction of labor was set. At the timeof induction the membranes were artificiallyruptured, and a fluidfilled open-tip catheter wasintroduced transcervically into the amniotic ca-vity for the recording of uterine activity. Anelectrode was attached to the fetal scalp forfetal heart rate monitoring. Uterine contrac-tions were induced with intravenous infusionof an incremental dose of oxytocin starting with2mU/min, until uterine activity of 150 — 200Montevideo units was obtained.

Tab. I. Medical reasons for exclusion of patients.

Obstetric History1. Cesarean section2. Perinatal death3. Vacuum or forceps delivery

Present Pregnancy1. Diastolic blood pressure > 90mmHg2. Gestational or type I diabetes mellitus3. Proteinuria4. Vaginal bleeding during the last trimester5. Premature rupture of membranes6. Polyhydramnios7. Sever anemia (hemoglobin concentration

< 6 mmol/1)8. Rhesus iso-immunization9. Recurring urinary tract infections

10. Any serious illness occurring during pregnancy

2.3 The reference group

In this group the beginning of labor was definedas the moment at which regular pains startedwith an interval of four to five minutes, oras the moment of spontaneous rupture of themembranes. Internal fetal monitoring was onlyused when fetal distress was suspected (n = 29)or when it appeared to be necessary to augmentuterine activity (n = 15).

2.4 Both groups

If necessary, a standard dose of 75 mg of pethi-dine-HCL I. M. was given for pain relief. Im-mediately after birth the infant was placed on

J. Perinat. Med. 13 (1985)


the mother's abdomen and the umbilical cordwas ligated. APGAR scores were determined atone and five minutes. The acid-base status wasdetermined from umbilical cord arterial bloodobtained immediately after delivery. On thethird post-partum day the bilirubin concentra-tion in serum was determined in all newbornswhich were still in the hospital. Neurologicalscreening according to PRECHTL [14] was per-formed in a random sample (n = 125). Thedevelopment of the infants was followed duringone year, using a "Psychomotor DevelopmentScheme 0-15 months" [16].All data were analyzed with a P. D. P. 11/70minicomputer using the Statistical Package for

Social Sciences System. Statistical analysis ofthe differences between the induction and refe-rence groups was performed with STUDENT'S t-test and with the X2-test, where appropriate.The SPEARMAN test was used to assess correla-tions between variables. A probability ofp < 0.05 was chosen to represent statistical si-gnificance.

3 Results

The composition of both groups is summarizedin Tab. II. A significant difference in the dura-tion of amenorrhea was found between theinduction and reference group. Both nullipa-

Tab. II. Age, parity and nationality of the women in the induction group (n = 184) and in the reference group(n = 156).

InductiongroupReferencegroup

Age<22

24(13.0%)15(9.6%)

23-27

87(47.3%)69(44.2%)

^ 28

73(39.7%)72(46.2%)

ParityNulliparous

60(32.6%)41(26.3%)

NationalityParous

124(67.4%)115(73.7%)

Dutch

160(87.0%)139(89.1%)

non-Dutch

24(13.0%)17(10.9%)

25-

20-

15-

10-

5-

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Fig. 1. Distribution of the times of delivery (hours) in the induction group (D) and in the reference group (·).



rous and parous women in the induction groupdelivered three days earlier than those in thereference group. Nearly 95% of the deliveries inthe induction group took place during daytime(8 — 18 hours) as compared to only 45% in thereference group (Fig. 1). The median value ofthe cervical ripeness score in the inductiongroup was 5.5 for nulliparous and 6.0 for pa-rous women. No significant correlation couldbe demonstrated between the cervix scores andthe duration of the first stage of labor. Thefirst stage of labor in the induction group wassignificantly shorter than that in the referencegroup (Tab. III).No differences in the duration of the second

..stage of labor were found between the groups.Meconium stained amniotic fluid occurred sig-nificantly less frequently in the induction groupthan in the reference group (2.7% vs. 8.3%).Medication for pain relief was significantly lessfrequently given in the reference group (24.4%)than in the induction group (49.5%). Three

women in the induction group and one in thereference group were delivered by cesarean sec-tion. In one patient the induction of labor couldbe held responsible for the necessity to performa cesarean section. In this patient, a partialabruptio placentae occurred immediatelyfollowing insertion of the intrauterine pressurecatheter. In the other two patients no relation-ship was apparent between the induction oflabor and the reason for cesarean section. Inthe induction group there was a significantlyhigher percentage of vacuum and forceps deli-veries (11.9%) than in the reference group(4.5%). Suspicion of fetal distress was the rea-son to terminate delivery in nine cases in theinduction group compared to two cases in thereference group. Lack of progression in thesecond stage of labor formed the indication toperform a vacuum or forceps extraction in 13women of the induction group as compared tofive women of the reference group. The amountof blood loss during labor and post partum didnot differ significantly between the two groups.

Tab. III. Duration of the first and second stage of labor in minutes (mean ± S. D.) in the various groups.

First stage n Second stage

Induction group nulliparousReference group nulliparousInduction group parousReference group parous

58*40*

123*115

349 + 138482 -1- 204268 + 121340 + 168

5840

123115

37 + 1838 + 2215 ± 11

•12±8

* Women who underwent cesarean section are omitted.

Tab. IV. Birthweights (median and range) and the APGAR scores and low umbilical arterial pH values in the variousgroups.

Induction groupnulliparousReference groupnulliparousInduction groupparousReference groupparous

n

58*

40*

123*

115

Birth weight(g)3400(2260-4410)3375(2573-4370)3468(2530-4410)3486(2710-4540)

Apgar-scores<7n

3

2

3

2

Umbilical arterialpH <7.15n

10

5

6

5

* Women who underwent cesarean section are omitted.



Tab. V. Serum bilirubin concentrations (mean ± S. D.) in the newborns on the third day and the number ofnewborns treated with phototherapy.

InductionReference

group (n =group (n =

184)156)

Bilirubinconcentration(μπιοΐ/ΐ)

130 ±56.2121 ±51.8

Infants with abilirubin concentration> 200 μηιοΐ/ΐn

1810

Infants receivingphototherapy

n

94

With regard to the newborns, no significantdifferences between birthweights, APGAR scoresand umbilical arterial blood gas values in thetwo groups were found (Tab. IV). There wasalso no significant difference between the neo-natal bilirubin values in the two groups (Tab.V).The results of the neurological screening in 67infants of the induction group were not diffe-rent from those in the 58 infants of the referencegroup. In the induction group nine infants(13.4%) were considered "suspect" as compa-red to seven infants (12.1%) in the referencegroup.The follow-up study of the infants during theirfirst year of life did not reveal any differencesbetween the groups. In both groups three chil-dren were suspected to have slightly impairedpsychomotor development, but no relationshipwith the mode of labor and delivery was appa-rent.

4 Discussion

The supposed greater safety of elective induc-tion as compared with spontaneous labor forboth mother and infant could not be confirmedin our study. Almost all electively induced wo-men were delivered during daytime. However,there is no reason to suppose that in our hospi-tal setting this fact had any influence on thequality of care. In both groups the conditionof the newborns was good. A less frequentoccurrence of meconium stained amniotic fluidin electively induced labor has also been repor-ted in other studies [5, 18]. The explanation of

this finding is not clear. latrogenic prematuritydid not occur in our study. Ultrasound exami-nation to confirm the duration of pregnancycan be considered of paramount importance toprevent this complication. The time with whichthe duration of pregnancy was reduced in wo-men with electively induced labor as comparedto women with spontaneous labor was onlythree days. This can be explained by the factthat induction was not started until the cervixwas considered to be "ripe". The finding ofa higher percentage of vacuum and forcepsdeliveries in the induction group could, in re-trospect, not be explained by a higher frequencyof fetal distress or a prolonged second stageof labor. The fact that fetal heart rate wascontinuously monitored in all women in theelective induction group could be an importantcontributing factor. It may also be possible thatthe obstetrician feels more responsible for agood result when labor is electively induced:"Having started the woman's labor electivelyand closely following it to full dilatation withfetal monitoring, the obstetrician may well feelthat he can ensure successful delivery by inter-vening in the second stage as well [22]". Theresults of the neurological examination of thenewborns and of the follow-up study did notreveal any differences between the infants inthe two groups, which is in agreement with theresults of other studies [6, 12].It is concluded that no somatic obstetric orneonatologic arguments against or in favor ofthe procedure of elective induction of labor canbe derived from the results of this study. Thedecision to electively induce labor must be ba-sed on other than somatic considerations.



Summary

Elective induction of labor is still a controversial ob-stetric procedure. The safety of the procedure and thepossibility to program labor during daytime is an oftenheard argument in favor of it. Also the possibility toprevent term intrauterine fetal death of unknown causeand the possibility to apply fetal monitoring from thebeginning of labor are put forward as arguments infavor of elective induction of labor. Feelings of un-naturalness and the dangers of prematurely induceddelivery are the most often heard arguments against it.We performed a prospective study to determine thedifferences between elective induction of labor andspontaneous labor. During 17 consecutive months agroup of 184 elective inductions was studied in theDepartment of Obstetrics, University Hospital —Dijkzigt, Rotterdam. Only healthy women with anuncomplicated pregnancy were included in the studygroup and all women were allowed a free choice ofelective induction or spontaneous labor. The referencegroup was composed by a system of "matched controls".For induction of labor a standard technique includingartificial rupture of the membranes and constant in-trauterine fetal monitoring was used. Oxytocin wasadministered intravenously in an incremental dose. Afterdelivery the acid-base status of the newborns was deter-mined, and part of the newborns were subjected toa neurological screening according to PRECHTL. Thedevelopments of the infants was followed during one

Keywords: Induction of labor, elective, oxytocin.

year using a "psychomotor development scheme 0 — 15months".The duration of pregnancy appeared to be three daysshorter in the induction group than in the referencegroup. Also, the first stage of labor was significantlyshorter in the induction group as compared to the ref-erence group. It appeared possible to program laboralmost exclusively during daytime. Meconium stainedamniotic fluid occurred significantly less frequently inthe induction group than in the reference group. In onepatient the induction of labor could be held responsiblefor the necessity to perform a cesarean section. Therewas a significantly higher percentage of vacuum andforceps deliveries in the induction group (11.9%) thanin the reference group (4.5%). No difference betweenbirthweights, APGAR scores and umbilical arterial bloodgas values in the two groups were found. Neither theneurological screening nor the follow-up study of theinfants revealed any differences between the two groups.We were not able to confirm the often postulated greatersafety of the procedure. A greater number of vacuumand forceps deliveries in the induction group could, inretrospect, not be explained by a higher frequency offetal distress in this group. This study did not providesound arguments against or in favor of the procedure ofelective induction of labor.It is concluded that the decision to electively inducelabor must be based on other than somatic con-siderations.

Zusammenfassung

Programmierte Geburt — eine prospektive klinische Stu-die, I.: geburtshilfliche und neonatologische AspekteDie programmierte Geburt ist in der Geburtshilfe weiter-hin ein kontroverses Thema. Weit verbreitete Argumentefür die Einleitung sind die Sicherheit der Methode unddie Möglichkeit, die Geburt während eines normalenklinischen Tagesablaufes zu programmieren. Auch dieMöglichkeiten, einen intrauterinen Tod unbekannter Ur-sache am Termin zu vermeiden sowie ein fetales Monito-ring von Geburtsbeginn an durchzuführen, sprechen füraktive, einleitende Maßnahmen. Dagegen sprechen Ar-gumente, die auf die ,Unnatürlichkeitc der Methode unddie Gefahr der Unreife bei induzierten Geburtsabläufenhinweisen. Wir führten eine prospektive Studie durch,um die Unterschiede zwischen programmierten undspontanen Geburten zu erfassen. In der Geburtsabtei-lung des Universitätskrankenhauses Dijkzigt, Rotter-dam, wurde innerhalb eines Zeitraums von 17 Monateneine Gruppe von 184 Frauen mit programmierter Geburtuntersucht. Die Gruppe umfaßte nur gesunde Frauennach unkomplizierter Schwangerschaft, denen freige-stellt war, ob sie sich für eine Einleitung oder eineSpontangeburt entscheiden. Die Referenzgruppe war

nach dem System der ,matched controls' zusammenge-stellt. Die Geburtseinleitung erfolgte nach standardisier-ter Technik mit Blasenpunktion und intravenöser Oxyto-cininfusion in ansteigender Dosierung bei konstantemintrauterinen, fetalen Monitoring. Post partum wurdeder Säure-Basen-Status der Neugeborenen untersuchtsowie ein Teil der Kinder einem neurologischen Screen-ing nach PRECHTL unterzogen. Während des ersten Le-bensjahres wurde die kindliche Entwicklung unter An-wendung eines ,psychomotorischen Entwick-lungsschemas 0—15 Monate6 verfolgt.Die Dauer der Schwangerschaft war in der Einleitungs-gruppe 3 Tage kürzer als in der Kontrollgruppe. Auchdie Eröffnungsperiode war in der Einleitungsgruppe si-gnifikant verkürzt gegenüber der Kontrollgruppe. Wiees scheint, werden Geburten fast ausschließlich währenddes Tages programmiert. Mekoniumhaltiges Fruchtwas-ser trat in der Einleitungsgruppe signifikant wenigerhäufig auf als in der Kontrollgruppe. Bei einer Patientinwar die Geburtseinleitung wahrscheinlich der Grund fürdie Notwendigkeit einer Sectio. Der Anteil an Vaku-umextraktionen und Zangenentbindungen war in derEinleitungsgrüppe deutlich höher als in der Kontroll-



gruppe (11,9% vs. 4,5%). Bezüglich des Geburtsge-wichts, des ApGAR-Scores und der Blutgaswerte in derNabelarterie unterschieden sich die Gruppen nicht.Ebenso ergaben weder das neurologische Screening nochdie Nachuntersuchungen Hinweise für Unterschiede zwi-schen den Gruppen.Wir können die oft postulierte Aussage, daß eine pro-grammierte Geburt sicherer ist, nicht bestätigen. Retro-

Schlüsselwörter: Oxytocin, programmierte Geburt.

spektiv kann die erhöhte Anzahl von Vakuumextraktio-nen und Zangenentbindungen nicht durch eine stärkereFrequenz von fetalem Distress in dieser Gruppe erklärtwerden. Diese Studie liefert keine schlagkräftigen Argu-mente für oder gegen eine programmierte Geburt.Wir meinen, daß die Entscheidung für eine program-mierte Geburt nicht auf der Basis rein medizinischerÜberlegungen getroffen werden kann.

Resume

Declenchement electif du travail: etude clinique prospec-tive, I: effets obstetricaux et neonatauxLe declenchement du travail est encore une procedureobstetricale contreversee. La securite du procede et lapossibilite de programmer le travail pendant la journee,sont des arguments souvent entendus en sä faveur. Lapossibilite d'eviter les morts foetales in utero ä terme decause inconnue et la possibilite de mettre en oeuvre lemonitoring foetal des le debut du travail sont egalementmis en avant comme arguments en faveur du declenche-ment du travail. Les arguments les plus souvent entenduscontre le declenchement sont le sentiment d'aller contrela nature et le danger d'induire un accouchement prema-ture. Nous avons realise une etude prospective afin dedeterminer les differences entre le declenchement dutravail et le travail spontane. Pendent 17 mois consecu-tifs, un groupe de 184 declenchements a ete etudie dansle d6partement d'Obstetrique, a Fhöpital universitaireDijkzigt de Rotterdam. On n'a inclu dans le groupeetudie que des femmes en bonne sante avec une grossessedepourvue de complication et toutes les femmes ont eule libre choix d'un declenchement du travail ou d'untravail spontane. Le groupe de reference a ete etabli parun Systeme «d'appariement controle». Pour le declenche-ment du travail, on a utilise une technique standardcomprenant la rupture artificielle des membranes et unmonitoring foetal intra-uterin permanent. L'ocytociquea ete utilise par voie intraveineuse a doses progressives.Apres 1'accouchement, on a determine I'equilibre acido-basique des nouveaux-nes et une partie des nouveaux-nes a ete soumise a un bilan neurologique de PRECHTL.On a suivi le developpement des enfants pendant un an

Mots-cles: Declenchement du travail, electif, ocytocine.

en se servant d'un schema de developpement psychomo-teur de 0 a 15 mois.La duree de la grossesse est plus courte de trois joursdans le groupe declenche que dans le groupe de referen-ce. Egalement, la premiere partie du travail est significa-tivement plus courte dans le groupe declenche en compa-raison avec le groupe de reference. II apparait possiblede programmer le travail presque exclusivement pendantla journee. L'apparition de liquide amniotique teinte demeconium est significativement moins frequente dans legroupe declenche que dans le groupe de reference. Chezune patiente, le doclenchement du travail peut etre tenucomme responsable de la necessite de realiser une cesa-rienne. II y a un pourcentage significativement plus elevede ventouse et de forceps dans le groupe declenche(11,9%) que dans le groupe de reference (4,5%). On n'apas trouve de difference entre les poids de naissance, lesscores d'ApGAR et les valeurs des gaz sanguins dans1'artere ombilicale dans les deux groupes. Ni le bilanneurologique, ni le suivi des enfants n'ont reveles dedifference entre les deux groupes.Nous ne sommes pas capables de confirmer la plusgrande securite souvent postulee de cette procedure. Lenombre plus eleve de ventouse et de forceps dans legroupe declenche, ne peut retrospectivement etre expli-que par une frequence plus elevoe de souffrances foetalesdans ce groupe. Cette etude ne fournit pas d'argumentpour ou contre le declenchement du travail. Les auteursconcluent que la decision du declenchement du travaildoit etre fondee sur des considerations autres que medi-cales.

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Received August 13, 1984. Accepted October 26, 1984.

Prof. Dr. H. C. S. WallenburgDepartment of Obstetrics and GynecologyErasmus University Medical School, Ee 2283P. O. Box 17383000 DR RotterdamThe Netherlands


elective induction of labor: a prospective clinical study

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