OPk - it's long I thought this was quite well written in that it details the differences between mums having their first babies and women having their subsequent babes.

Results: Clinical Obstetrics and Gynecology

(C) 2007 Lippincott Williams & Wilkins, Inc.

Volume 50(2), June 2007, pp 537-546

Elective Induction: When? Ever?
[Current Controversies in Obstetrics: What Is an Obstetrician to Do?]

GROBMAN, WILLIAM A. MD, MBA
Department of Obstetrics and Gynecology, Northwestern University Medical School,
Chicago, Illinois
Correspondence: William A. Grobman, MD, MBA, 333 East Superior Street, Suite
410, Chicago, IL 60611. E-mail: w-grobman@northwestern.edu

----------------------------------------------

Outline

Abstract

Analytical Boundaries of the Present Article

The Importance of Well-established Gestational Age

Does Elective Induction Increase the Rate of Cesarean Delivery?

Are Elective Inductions of Labor Associated With Differences in Maternal
Pregnancy Outcomes Other Than the Cesarean Delivery?

Are Elective Inductions of Labor Associated With Differences in Perinatal
Outcomes?

Are Elective Inductions of Labor Associated With an Increase in Health Care
Interventions or Costs?

What are the Limitations of an Observational Study Design in Assessing the
Ramifications of Elective Labor Induction?

Are the Results From Investigations With Nonobservational Study Designs
Consistent With Results From Studies With Observational Designs?

In the Final Analysis, Who is a Candidate for an Elective Induction of Labor?

References

Abstract

The frequency of labor induction has increased significantly in recent years.
Although medically indicated inductions comprise a portion of this increase,
elective inductions have increased in frequency as well. Given that elective
inductions, by definition, provide no benefit from a strictly medical standpoint,
it is particularly important to evaluate whether women who undergo these
inductions incur greater risks than those who labor spontaneously. This article
will assess whether elective inductions are associated with changes in pregnancy
outcomes, and evaluate how these associations are influenced by parity and
cervical ripeness.

----------------------------------------------

The number of labor inductions in the United States has markedly increased in
recent years. Although approximately 1 in 10 women had labor initiated by
induction in 1990, nearly 1 in 5 women underwent labor induction by 1998.1
Multiple reasons are likely to account for this increase. There is some evidence
that patients are receiving a greater number of routine ultrasound examinations
in the first and second trimester, thereby providing physicians with greater
confirmation of gestational age and the information needed to prevent unexpectedly
postdate pregnancies through properly timed labor inductions. Also, there is
some evidence that physicians are willing to induce labor more readily when
evidence of medical complications arises during pregnancy. Analyses, for
example, have revealed that labor inductions have increased, not just for women
with term gestations, but also for women with preterm gestations.2 Given the
high likelihood that a preterm induction of labor is undertaken only for
perceived medical necessity, this trend of increasing preterm inductions should
indicate a greater willingness on the part of obstetric providers to hazard
neonatal risks of prematurity rather than fetal risks in a continuing pregnancy.

Nevertheless, there is evidence that medical inductions are not wholly
responsible for the dramatic increase in the frequency of induced labor. Zhang
et al 1 have documented that the frequency of elective inductions has also
risen. This finding should cause the obstetric community some pause. By
definition, an elective induction of labor has no indication and provides no
benefit from a strictly medical standpoint. That does not necessarily imply that
there may not be reasons, such as convenience, for women or physicians to desire
an elective labor induction. And, if there were to be no medical risk, there
would seem little reason for a patient or physician to pause before proceeding
with an elective labor induction. Yet, if there were increased risks from an
elective induction, the lack of a medical benefit would argue against its use as
a routine obstetric intervention. In deciding whether elective induction of
labor is ever (and if so under what circumstances) a reasonable plan of care,
therefore, the question that must be asked is simply: "Does an elective
induction increase adverse outcomes when compared with spontaneous labor?" In an
effort to answer this question, I will first review the data from observational
studies associating elective labor induction with cesarean. Other associations
of elective induction with both maternal and neonatal outcomes will then be
examined, as will the relationship between elective induction and resource
utilization. Lastly, I will review the nonobservational studies that have
attempted to assess the relationship between elective induction of labor and
pregnancy outcomes.

Analytical Boundaries of the Present Article

As noted above, elective inductions are those that are undertaken without
definite medical indications. The present analysis will only attempt to address
the benefits and risks of these types of inductions, and not attempt to
investigate disputes regarding whether certain types of inductions are truly
medically indicated or actually elective. For example, there presently is
controversy as to the optimal gestational age at which delivery should occur in
an effort to minimize perinatal complications. Some experts have argued for 41
weeks whereas others have argued for 42 weeks. The purpose of this article is
not to examine that particular controversy (ie, whether 41 wk is actually a
medical indication for labor induction) or others like it, but only to address
whether and under what circumstances it is appropriate to proceed with
inductions that are clearly and overtly elective without any valid medical
indication.

The Importance of Well-established Gestational Age

Given that elective inductions, by definition, do not provide clear advantage
for the neonate, it is crucial that the induction should not be initiated under
circumstances that inherently increase the risk of neonatal morbidity. It goes
without saying, for example, that a clearly preterm gestational age is a
contraindication to elective induction given the risks of prematurity that a
neonate might encounter. Yet, there is evidence in the literature of neonates
who have suffered from iatrogenic prematurity due to elective deliveries
initiated under the mistaken assumption that a mature gestation had been
achieved. For example, Flaksman et al 3 documented 32 neonates referred to their
center who were iatrogenically premature. Related morbidity was not minimal: 24
neonates had respiratory distress syndrome, 9 had a pneumothorax or pneumomediastinum,
and 1 died. Studies such as this have led to the ACOG guidelines which set the
conditions for a gestation to be considered term and not contraindicated from
having an elective delivery.4 These confirmatory conditions are (1) documented
fetal heart tones for 20 weeks by fetoscope or 30 weeks by Doppler; (2) 36 weeks
since the appearance of a reliably positive urine or serum human chorionic
gonadotropin test; (3) 39 weeks of gestation supported by a 6 to 11 weeks
crown-rump length; (4) 39 weeks of gestation supported by a 12 to 20-week
ultrasound with a confirmatory history. Despite the publication of this list,
there is evidence that elective deliveries continue to occur even though these
criteria (or documented fetal lung maturity by amniocentesis) have not been
met.5 This practice is difficult to justify, and given even a small risk of
iatrogenic prematurity, an elective delivery should not take place unless fetal
maturity has been confirmed by established guidelines.

Does Elective Induction Increase the Rate of Cesarean Delivery?

Multiple investigators have attempted to discern whether elective induction of
labor changes the probability of cesarean delivery. In the large majority of
these studies, investigators have used cohort study designs, and compared women
who have been electively induced with those who arrive at the hospital in
spontaneous labor. There have also been a smaller number of randomized trials
that also have attempted to assess the association of labor induction with
cesarean delivery. Before reviewing these studies in detail, one point is
important to make: answering the question of whether elective induction
increases the chance of cesarean can only be done meaningfully if one further
specifies what population is under consideration. Nulliparous and multiparous
women (specifically those with a prior vaginal delivery) are so different with
regard to their baseline risk of cesarean and potentially with regard to the
association of induction with cesarean that a nonstratified study of a
population of mixed parity is all but impossible to interpret.6 Similarly, the
ripeness of the cervix consistently has been shown to be strongly associated
with the chance of cesarean delivery after labor induction.7 Thus, in trying to
understand best the association of induction with ultimate route of delivery,
one optimally would like to be able to stratify the study population by cervical
status at time of admission for labor induction.

The many observational studies that have been performed consistently reveal that
nulliparous women who undergo elective induction of labor are more likely than
their spontaneously laboring counterparts to have a cesarean delivery. Some
investigators have used patient information derived from large public databases
to assess the risk from elective induction of labor. For example, Dublin et al 8
linked birth certificate data with hospital discharge information from
Washington State to identify a large group of women for study. Among the 1017
nulliparous women who had a labor induction "without an identified indication,"
19.4% experienced a cesarean delivery; among the 3603 nulliparous women in
spontaneous labor, only 9.9% experienced a cesarean. Correspondingly, the
relative risk for cesarean associated with labor induction was 1.77 (95%
confidence interval 1.50-2.08), and this significant increase remained after
adjusting for potential confounding variables. Using a different technique for
patient identification, Seyb et al 9 found similar results. Instead of a public
database, these authors prospectively identified nulliparous patients as they
arrived on labor and delivery, thus reducing the possibility of ascertainment
bias. In this study group, consisting of 143 women undergoing an elective
induction and 1124 women in spontaneous labor, the risks of cesarean were 17.5%
and 7.8%, respectively. After adjusting for confounding variables, the final
odds ratio for cesarean delivery associated with elective induction was 1.89
(95% confidence interval 1.12-3.18).

Neither of these studies categorized nulliparous women by their cervical status
upon admission. Of those studies that have, there is consistent evidence that a
woman with an unfavorable cervix at the start of labor induction has a
particularly increased risk for cesarean associated with that induction. Thus,
when comparing 4635 nulliparous women in spontaneous labor with 2647 nulliparous
women who underwent induction, Johnson et al 10 found an increased risk of
cesarean associated with any labor induction (adjusted odds ratio 1.77, 95%
confidence interval 1.46-2.11), and this risk was further increased when the
induction occurred in the presence of an unfavorable (ie,

The lower background risk of cesarean in a multiparous population has made it
all the more difficult to evaluate whether elective labor induction is
associated with cesarean delivery in this population. Dublin et al,8 who did
analyze several thousand multiparous women, concluded that these women were not
at increased risk of cesarean after elective induction. These data were not
stratified by cervical ripeness. Yeast et al,11 who did stratify by cervical
ripeness, concluded that there was an increased risk of cesarean for multiparous
women who underwent an induction with either a ripe or unripe cervix, although
they performed this stratified analysis for women undergoing both elective and
indicated inductions. Other authors who have limited their study populations
only to those women undergoing elective induction have frequently found a risk
of cesarean that was higher among multiparous women being electively induced
than among those in spontaneous labor, but the sample sizes have been such that
these results have not reached statistical significance. Thus, Boulvain et al 15
found a 40% higher risk of cesarean associated with elective induction and
Heinberg et al 16 noted a nearly 50% higher risk of cesarean with elective
induction in the presence of an unfavorable cervix but neither of these
differences reached statistical significance, as the studies were underpowered
to do so. Ultimately, these observational trials do not allow one to conclude
that elective induction is associated with an increase in the risk of cesarean
among multiparous women, although the evidence that does exist, particularly for
women with an unfavorable cervix, suggests that the possibility of a clinically
significant increase cannot be dismissed.

Are Elective Inductions of Labor Associated With Differences in Maternal
Pregnancy Outcomes Other Than the Cesarean Delivery?

Several authors have documented other maternal outcomes which may differ
depending on whether labor is spontaneous or electively induced. For example,
Dublin et al 8 noted that instrumental deliveries were more common among women
who were electively induced (odds ratio 1.20, 95% confidence interval 1.09-1.32).
Although this odds ratio was derived from a group of women with mixed parity,
the authors stated that the effect size did not differ significantly according
to parity. Studying only nulliparous women, Cammu et al 17 noted a similarly
increased risk of instrumental delivery (odds ratio 1.09, 95% confidence
interval 1.04-1.14). Another health outcome that has been noted by several
authors to differ among women who are electively induced is the amount of
postpartum bleeding. Using a case control design, Sheiner et al 18 compared
women who had a postpartum hemorrhage with those who did not. After adjusting
for multiple confounding factors, they found that postpartum hemorrhage was
significantly associated with labor induction.18 Vrouenraets, who studied only
nulliparous women, determined that this increased blood loss corresponded to an
increased risk of transfusion.13 In their cohort, 10.6% of women who were
electively induced received a blood transfusion, a frequency significantly
higher than the 5.8% of spontaneously laboring women who received a transfusion.

Are Elective Inductions of Labor Associated With Differences in Perinatal
Outcomes?

There is little consistent evidence that elective induction of labor among women
with properly dated gestations is associated with any significant change in
adverse perinatal outcome. Many authors of observational studies have noted that
women who are electively induced have a lesser risk of meconium at delivery.8,19-21
Nevertheless, there has not been any demonstration that this lesser frequency of
meconium translates into any lesser risk of related adverse outcomes, such as
meconium aspiration syndrome. The study by Yeast et al 11 indicates that
neonates of multiparous, but not nulliparous women, who were electively induced
were less likely to be admitted to the intensive care nursery. Other authors,
however, have not found a similar association.8,19,20 Also, there has not been
any good evidence that elective labor induction after achievement of fetal
maturity changes the risk of significant neonatal morbidity or mortality.

Are Elective Inductions of Labor Associated With an Increase in Health Care
Interventions or Costs?

There has been some evidence that women who are electively induced spend a
greater amount of time in the hospital before delivery. For example, both Seyb
et al 9 (studying only nulliparous women) and Maslow and Sweeny 21 (studying a
population of mixed parity), noted that women who were electively induced had
admission-to-delivery times on labor and delivery that were 3 to 4 hours longer
than their spontaneously laboring counterparts. Vahratian et al 12 stratified
nulliparous women and multiparous women, respectively, by cervical ripeness in
an effort to assess if changes in the labor curve were associated with labor
induction in different subpopulations. What is clear from their data is that
both nulliparous and multiparous women who were induced with unfavorable
cervices had significantly longer labors than those who were induced with
favorable cervices. These authors did not, however, compare total time in labor
and delivery for the induced women with spontaneously laboring women.

Other authors have documented particular resources which are used more
frequently by women undergoing induction. Many investigators have noted that
labor induction is associated with an increased use of epidural anesthesia,15,17,19,20
and this increase remains present regardless of parity or cervical status.12,21
In his cohort of mixed parity, Glantz 20 also found internal monitoring to be
significantly more common among women who were electively induced. Van Gemund et
al 19 additionally found that electively induced women were more likely to have
fetal scalp blood sampling.

In an effort to evaluate overall resource utilization, rather than individual
components, several authors have assessed the association of elective induction
with summated costs of peripartum care. In the analysis of nulliparous women,
Seyb et al 9 found that those who were electively induced incurred costs that
were 17.4% higher than those in spontaneous labor. The additional expenses were
not due to additional outlays of one particular health resource, but were
significantly greater in all the costs centers (such as pharmacy and labor and
delivery) that were examined. Maslow and Sweeny 21 demonstrated that these
increased costs were not merely due to an increased number of cesarean
deliveries. In their study, they determined that the inpatient costs of women
who had vaginal deliveries after elective inductions were approximately 25%
higher than those of women whose vaginal deliveries occurred after spontaneous
labors. Allen et al,22 studying a Canadian cohort of low-risk nulliparous women,
noted an increase in costs associated with induction that was similar in
magnitude to that of Maslow and Sweeny.21 In none of these studies were cost
differentials further stratified by cervical status at initiation of labor
induction.

What are the Limitations of an Observational Study Design in Assessing the
Ramifications of Elective Labor Induction?

As noted above, the large majority of observational studies have used a cohort
design in which the outcomes of those with an exposure (ie, labor induction) are
compared with the outcomes of those without the exposure (ie, spontaneous
labor). In such a design, it is crucial to ensure that any subject has the
potential to be in the exposed or nonexposed group. In the case of labor
induction, although it is true that any one woman may have an induction or
experience a spontaneous labor, it is not true that she may experience either of
these events at a similar time. If a woman is not electively induced at 39
weeks, there is not a guaranteed alternative of immediate spontaneous labor.
Thus, a comparison of outcomes in women who are electively induced at 39 weeks
with outcomes of those who are in spontaneous labor at 39 weeks will not
necessarily elucidate what outcomes would have been for women if they had not
been induced.

Are the Results From Investigations With Nonobservational Study Designs
Consistent With Results From Studies With Observational Designs?

There have been few randomized trials that have compared elective labor
induction with expectant management.23-28 None of these trials have demonstrated
differences between the groups with regard to outcomes such as cesarean
delivery, operative vaginal delivery, or other maternal or perinatal morbidity.
However, these trials were all relatively small, with the largest containing
only 264 randomized women, and were correspondingly underpowered to detect
differences even if they did exist. For example, although Martin et al 24 and
Sande et al 27 found that women who were induced had risks of cesarean that were
approximately 4 to 6 times higher, respectively, than those who were expectantly
managed, neither author was able to demonstrate that these differences were
statistically significant.

None of these studies have included detailed analyses of costs or resource
utilization. In some trials, lengths of labor have been documented, and the
results are conflicting. Amano et al 26 and Nielsen et al,28 for example, showed
that induced women had shorter first stages of labor than women who were
expectantly managed, whereas Martin et al 24 reported that the total length of
labor was longer in the electively induced group. Some of this conflict may be
due to study populations of different characteristics. Amano et al 26 studied
only nulliparous women without stratifying by cervical ripeness, Nielsen et al
28 studied a population of mixed parity with only favorable cervices, and Martin
et al 24 examined a population of mixed parity and varying cervical ripeness.

Given that prospective comparisons of elective induction with expectant
management have been underpowered, have not provided stratified results for
different subpopulations (eg, multiparous women with a favorable cervix), and
have not reported on economic outcomes, Kaufman et al 6 attempted to use a
decision analytical model to assess both health and cost consequences of
different management strategies. The advantage of such an analytical model is
that it allows estimation of outcomes of multiple different strategies among
multiple different populations. Thus, they were able to compare outcomes after
the decision to induce labor or expectantly manage the pregnancy, evaluate how
these outcomes depended upon the week of gestation when the management decision
was made, and stratify the outcomes by parity and cervical ripeness. Their
analysis revealed that regardless of parity or cervical status, undertaking an
elective induction incurs costs to the medical system. Not surprisingly, these
costs were greater for nulliparous women than for multiparous women. Also, using
baseline estimates, cesarean deliveries were more likely in all subpopulations
after an elective induction. As with the economic costs, the increase in
cesareans was greater among nulliparous women or those with an unfavorable
cervix. Of note, the number of extra cesareans incurred by proceeding with labor
induction was on the order of thousands per 100,000 women for all groups with
the exception of multiparous women with favorable cervices. In this group, under
baseline assumptions, 167 additional women would have a cesarean for every
100,000 who were induced; in sensitivity analysis, however, even this relatively
small number of additional cesareans incurred by labor induction did not
persist, and under some assumptions, labor induction actually resulted in fewer
cesareans.

In the Final Analysis, Who is a Candidate for an Elective Induction of Labor?

Several points seem clear from the available data. First, without clear
confirmation of a gestational age of at least 39 weeks or another indication of
fetal maturity, elective labor induction cannot be supported. Second, regardless
of parity, women with an unfavorable cervix at the time of elective induction of
labor have been found to have longer labors, use a greater amount of health care
resources, and have a greater number of cesareans than women with a favorable
cervix at elective induction of labor. Third, when induced, nulliparous women
have longer labors, use a greater amount of heath care resources, and have a
greater number of cesareans than multiparous women. Indeed, in observational
studies that contain a sufficient number of subjects limit the possibility of
type II error, authors have consistently found that elective induction of labor
in nulliparous women, even with a favorable cervix, is associated with an
additional risk of cesarean delivery. This finding has not been as consistent
for multiparous women, and certainly for multiparous women with a favorable
cervix. These conclusions are based largely on observational trials and
supported by decision analytical models that have been performed. Unfortunately,
confirmatory results from randomized trials are lacking, as the only trials that
have been done with this type of study design are too underpowered to provide
clear guidance.

As care givers, our first priority is to do no harm. Given that, by definition,
elective induction of labor provides no medical benefit to a woman or her child,
we should only proceed with this intervention if the available evidence
indicates that we will not incur additional risk to our patients. At this point
in time, the evidence that exists does suggest that there may be additional
risks from elective labor induction for any woman with an unfavorable cervix, as
well as for nulliparous women with a favorable cervix, and accordingly, it would
seem most ideal to avoid elective induction of labor in these women. On the
other hand, elective induction of labor has not been clearly shown to have
detrimental associations for multiparous women with favorable cervices, and it
seems, for women with these characteristics who meet appropriate gestational age
criteria, that elective induction of labor is an acceptable option.

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Key words: elective labor induction; cesarean; pregnancy outcomesAccession
Number: 00003081-200706000-00022