Side
Effects of Epidurals: Research Data
Author’s
note:
All of the following data, unless otherwise cited, is collected and summarized
from three recent reviews of this topic. This article is intended as a summary
of available data. For more complete information, you are encouraged to seek
out the original review articles, and to further trace them back to the
original studies they review.
Please
note the section at the end on “limitations of research data.” Also, note that
the risks illustrations only include risks, and do not cover benefits or
treatment implications.
See
also the summary chart on the
parent education part of the website, which covers ways to prevent and treat
side effects.
Janelle
Durham
Some
terms used in the summaries below
·
Relative
risk (RR). The chance of this side effect occurring in women who have had in
epidural in labor versus women who have not. For example, a RR of 2.0 means
that women who have an epidural are two times more likely to have this side
effect.
·
Randomized,
controlled trials (RCT). Participants in a study (laboring women) are randomly
assigned to either the epidural group, or the no epidural group. The no
epidural group may receive no medication or may receive another treatment such
as parenteral opioids (e.g. IV narcotics). After treatment, the two groups are
compared, differences in outcomes are assumed to be due to epidural use.
o
Intent
to treat: analysis is based on what group the participants were originally
assigned to, no matter what medication they actually ended up receiving during
labor.
o
Crossover.
With epidural studies included in Lieberman’s review, of those assigned to
“epidural groups”, 2 - 35% of the members never actually received an epidural.
Of women assigned to “no epidural groups”, as many as 56% of the participants
chose to get an epidural. So, intent to treat analyses may not really reflect the
impact of epidural.
·
Observational
studies: After the participants have given birth, studies are done which
compare the side effects experienced by women who had epidurals with women who
did not, and conclusions are drawn about what effect the epidural had on these
women.
·
Meta-analysis.
Leighton combined results from 14 studies to give a broad summary of the
likelihood of various side effects.
Effects
on the Laboring Mother
·
Pain Relief:
o
Trials
evaluated pain relief using a visual analog scale: patients are asked to mark
on a scale how strong their pain is, from 1 (no distress) to 100 (unbearable
distress). Meta-analysis indicates that with epidural, pain ratings were an
average of 40 points lower during first-stage, and 29 points lower during
second stage. (Leighton)
o
Philipsen
and Jensen found that 59% of the women in the epidural group reported a
“painless” labor and delivery
·
Patient satisfaction:
o
Philipsen
and Jensen found that 73% of women who used epidural would choose it for
subsequent labors.
o
Lower satisfaction
for those who had planned natural childbirth: In Kannan’s study of
47 women who had planned not to use pain medication during childbirth, 23 women
did not use medication, and 24 chose epidural. The women who requested epidural
reported significantly lower pain scores. However, 88% of them reported being
less satisfied with their birth experience than those who did not use epidural,
despite lower pain intensity.
·
Incomplete pain
relief:
“In spite of large doses epidural block may fail to provide
adequate analgesia in up to 25% of patients due to difficulty in blocking
sacral roots.” (Eldor, J. Combined Spinal-Epidural Anesthesia? On CSEN, the
Global Regional Anesthesia website. http://www.csen.com/anesthesia/book/#ch11)
·
Hypotension (low blood pressure).
16 studies: 0 – 50%. (Mayberry)
Meta-analysis: RR: 74.2 (Leighton*)
o
Risks: Can cause decreased
oxygen flow to fetus, decreased fetal heart rate.
o
Benefits: This side effect is
generally considered a risk of epidural, but it may be a benefit in certain
cases of maternal hypertension.
·
Fever > 38°C or
100.4 °F.
o
4
RCT’s, 6 observational: Without epidural, 0 – 5%. With: 4 – 24%. RR: 1.5 to
70.8 (Table VIII in Lieberman)
Meta-analysis: RR 5.6 (Leighton*)
o
The
rate of fever increased with longer labors, from 5% with labor < 3 h to 28%
with labor > 6 h. (Gonen) Typical increase of .07 degrees C per hour of
epidural. (Vinson)
o
Lieberman
et al and Gonen et al found that more than 95% of fever in their term
populations occurred in women who had received epidural. Epidural-related fever
is generally believed to result from thermoregulatory alterations rather than
infection. (Lieberman)
o
Secondary
effects / risks of fever (from Lieberman):
§
Increased risk of
instrumental / c-s:
One study showed women with temps > 99.5°F were 3 times as likely to have a
c-section (25% vs. 7%) and 3 times more likely to have instrumental delivery
(25% vs. 9%)
§
Mom assumed to have
infection, treated with antibiotics: 3 times more likely with epidural (20% vs.
6%)
§
Neonatal outcomes: Infants of women
with fever were 3 times more likely to have 1 minute Apgars <7, and 10 times
more likely to be hypotonic after delivery; 4 times more likely to require bag
and mask resuscitation, and 6 times more likely to be given oxygen in nursery.
·
Impaired motor
ability.
8 studies used the Bromage scale to assess leg strength or the rectus abdominus
muscle test to assess ability to sit up. The overall incidence of no motor
block or minimal motor block was high, 76 – 100%. This indicates that women
would be able to move around or walk with an epidural; however, in Olofsson,
considerably less than one third of women chose to be out of bed, citing
fatigue or a feeling of insecurity. (Mayberry)
·
Inability to Urinate. 3 studies: 0 – 68%
(Mayberry) Reason for concern: A full bladder may impede uterine contractility,
may cause bladder trauma, or a lack of postpartum bladder tone. Treatment:
Catheterization.
·
Nausea and vomiting. 7 studies examined
nausea: 0 – 30%, average is 7.3%. 5 studies examined vomiting: 0-13%, average
is 4.6% (Mayberry) Meta-analysis: 1.46 – slightly more likely with epidural
than without. (Leighton*)
·
Shivering. 2 studies examined:
only one case was documented in each study. (Mayberry)
·
Pruritus. (Itching.) 17
studies examined this: When 1 or more opioids was included in the medication
given, incidence ranged from 8 – 100%, with an average of 62%. When no opioid
was given, incidence was 0-4%. Most cases appeared to be mild, as very few
mothers requested treatment for itching. (Mayberry)
·
Sedation / Drowsiness. 5 studies: 1 – 56%,
average 21%. (Mayberry)
·
Perineal lacerations
(3rd and 4th degree). 6 studies: Without epidural – 3-34%.
With epidural – 5 to 37%. Relative risks: 1.0 – 2.7. (Lieberman) Severe
lacerations are more likely with instrumental delivery, and since data support
an increased risk of instrumental delivery with epidural, these increases are
likely closely related.
Effects
on the Fetus during Labor
·
Fetal Malposition
(occiput posterior, transverse). 3 RCT’s: 1) 19% with epidural vs. 4% without,
2) 22% vs. 18% 3) 16% vs. 14%. However, trials 2 and 3 had high crossover
rates, making those numbers harder to interpret. 2 observationals. Overall,
relative risk ranges from .8 to 4.2. (Lieberman, table IX.) It’s unclear whether
epidurals cause malposition, or whether women with a malpositioned baby are
more likely to choose epidural because of increased pain.
·
Fetal heart rate
abnormalities. Meta-analysis of 4 studies: no significant
difference with epidural. (Leighton*)
·
Tachycardia / Fetal
heart rate greater than 160 bpm. Rojansky et al: At the end of first stage: 7% with epidural vs. 2% without.
In second stage: 16% with epidural, 13% without. Mayer et al: 6% vs 0%.
(Lieberman) Likely due to increased risk of maternal fever, as FHR is highly
correlated with maternal temperature.
·
Bradycardia / Fetal
heart rate <100: after 11% of initial
or repeat injections of anesthetic into epidural space. (Stavrou 1990, cited in Thorp)
·
Fetal heart rate:
Late or variable decelerations Rojansky: end of first stage: 47% vs. 13%,
relative risk 3.3. Second stage: 66 vs. 41%, relative risk 1.6. (Lieberman)
·
Meconium stained
amniotic fluid.
None of 5 studies found any difference in meconium staining between epidural
and non-epidural groups (Lieberman)
Effects
on the Progress of Labor
·
Increased use of
oxytocin to stimulate contractions and speed labor. 5 randomized
controlled trials representing 3679 women: For women receiving narcotic
analgesia, oxytocin rates were 11 – 64%. For women receiving epidurals,
oxytocin rates were 27 – 78%. Mayberry’s analysis indicates augmentation is
1.28 times more likely with epidural. (Mayberry) Meta-analysis: RR 2.8
(Leighton*)
·
Decreased rate of
dilation Thorp, et al. Before epidural, both
randomized groups dilating at an average of .52 cm/hr. After analgesia,
epidural group was 1.9 cm / hr versus 2.7 cm / hr without epidural. (cited in
Lieberman)
·
Diminished urge to
push / decreased ability to actively push during 2nd stage. Mayberry describes this
issue, but does not state the incidence (how commonly it occurs). For care recommendations, see below.
·
Longer labor overall. 3 RCTs: .9, 1.5, and 2.4 hours longer with
epidural. 7 Observational: 1.7 to 5.1 hours longer. (table VI and VII in
Lieberman)Note: differences in length of labor between studies can depend on
issues like: whether start time is based on admission to the hospital,
frequency of contractions, or a particular cervical dilation.
·
Longer first stage. 6 RCT’s: -0.4 to
2.6 hrs longer. 11 observational: .6 to 4.8 hrs longer. (table VI / VII in
Lieberman) Meta-analysis: 26 minutes
longer on average. (Leighton*)
·
Longer second stage. 7 trials: all found
longer second stage, with the difference ranging from
Effects
on Mode of Delivery
·
Reduced chance of
spontaneous vaginal delivery (no cesarean or instrumental delivery needed) 6 of 9 studies
indicate that less than 50% of women who received an epidural had a spontaneous
vaginal delivery (Lieberman)
·
Instrumental vaginal
delivery (forceps and vacuum extractor).
o
Rate
without epidural ranges a great deal: 4% to 60% depending on the study.
(Lieberman)
o
10
RCTs: Rates 7 – 80%with epidural. RR 1.1 – 5.3.
(Crossover rates affect the accuracy of these results.) Observational
studies: 26 out of 27 showed a statistically significant association between
epidural and instrumental delivery. Rates: 6 – 76%. Relative risk ranged from
1.3 to 4.8. (Lieberman)
o
Meta-analysis:
RR of 2.08. (Leighton*)
o
Observational
studies limited to women with vaginal births indicate that 3-23% of women
without epidural had instrumental deliveries, vs. 5 – 52% of women with
epidural, leading to RR 1.7 – 14.0. (table V in Lieberman.)
·
Cesarean section (for
any reason) Meta-analysis
indicated No significant difference between patients randomized to receive
parenteral opioids and epidurals. (Leighton. See note above about concerns
about the accuracy of this analysis.*)
·
Cesarean for
non-reassuring fetal status: 5 RCT’s and 7 observational studies: There is not a
significantly higher rate for women with epidural versus for women without
epidural (Lieberman)
·
Cesarean for dystocia
/ failure to progress.
o
Summary:
§
10
RCT’s show relative risk ranging from .7 to 11.2 (c-section .7 times less
likely to 11.2 times more likely with epidural anesthesia than without.) Note that crossover rates influenced several
of these results.
§
33
observational trials show RR’s from 0 to 6.5.
(Of the 10 observations of low risk nulliparas in spontaneous labor,
RR’s ranged from 1.6 – 6.5.) The general trend of studies indicates a potential
increased risk of c-section; however, because epidurals are something that
laboring women choose, it is not clear whether epidural itself increased their
chance of c-section, or whether there was something inherent about these births
that would have made c-section more likely even without epidural (e.g. the
specific populations studied, the type of labors which lead mothers to choose
epidural, the specific setting for care, or the management of the labors) (Lieberman)
o
More
details on studies:
§
Highest relative risk
found in RCT: Thorp’s
RCT of 93 women (where only one woman in the no epidural group received an
epidural) found an 11-fold increase in cesarean rate amongst epidural group,
and stopped the trial early because of this finding.
§
Lowest relative risk
found in RCT: .7
in
§
A study which
controls for some additional factors: Lieberman et al (1996) evaluated 1733 term,
low-risk women with spontaneous onset of labor. The overall cesarean delivery
rate was 4% for women without epidural, and 17% with epidural. They divided
them into five groups based on characteristics which predict the choice to have
an epidural: such as dilation at admission, station of fetal head at admission,
rate of dilation, gestational age, infant birth weight, mother’s race, weight,
and height. In all 5 groups, the cesarean delivery rate was higher among women
who received an epidural, suggesting that the association was present
regardless of the characteristics of a woman’s labor. In a logistic regression
analysis controlling for these factors, epidural was associated with a 3.7 fold
increase in the rate of cesarean. (cited in Lieberman 2002)
Effects
on Maternal Postpartum Recovery
·
Postpartum hemorrhage
and retained placenta.
At one hospital, no difference. At a second hospital, risk of postpartum
hemorrhage was 15% with epidural and 3% without. Another study found the rate
of postpartum hemorrhage was twice as high among women who received epidurals
(10% vs. 5%) Amongst women with retained placenta, 51% had used epidural.
(Lieberman)
·
Postpartum urinary
retention.
2 studies of symptomatic urinary retention requiring treatment: 4% with
epidural, 1% without; 2.7% with, .1% without. 4 studies of asymptomatic (i.e. a
high residual volume in the bladder after voiding): 2 studies found no
association, 1 a RR of 1.8, one RR of 4.7 (Lieberman)
·
Urinary incontinence.
Viktrup and Lose: Immediate postpartum - 27%
with epidural vs. 13% without. At 3 months, 16% vs. 4%; at one year, 7% vs. 3%.
(cited in Lieberman)
·
Backache (long-term) 5 studies: current
data do not support an association with epidural (Lieberman) Macarthur et al
found more back pain with epidural on day 1 postpartum (53% vs. 43%), but no
difference on day 7, week 6, or at 1 year. (cited in Leighton)
·
Postpartum Headache. 2 studies indicate
that inadvertent dural punctures occur in 1.6 – 1.8% of women; 23% of these
women had new onset of chronic symptoms including headache, migraine, or neck
ache, starting within 3 months after childbirth, and lasting from nine weeks to
over 8 years. (Thorp) Mayberry states that these headaches can be severe enough
to temporarily interfere with women’s normal activities, including infant care
for up to 48 hours.
Effects
for the Newborn Baby
·
Apgar scores <7 at
1 minute, 5 minutes.
·
Low Umbilical cord
pH. 6
RCT’s and 4 observationals: No study found a significant difference with or
without epidural. (Lieberman) Meta-analysis of 5 studies shows no significant
difference (Leighton*)
·
Neonatal evaluation
for bacterial infection and/or neonatal antibiotic treatment. Lieberman: Neonates
whose mothers’ had epidurals were more likely to be evaluated for sepsis (34%
vs. 9.8%) and to be treated with antibiotics because of suspicion of sepsis
(15.4% vs. 3.8%) However, the rate of sepsis was low in both groups (.3%
epidural, .2% non-epidural) Philip: sepsis evaluation 25% with epidural, 16%
without; antibiotics 19% with, 11% without.
·
Hyperbilirubinemia (jaundice). 7
studies: All found 1.5 to 2.0 – fold
increase in the rate for infants after epidurals. (Lieberman)
·
Neonatal behavioral
and neurologic outcomes. 11 studies examined:
o
In
the 6 studies that examined epidural vs. no/minimal medication, 3 found no
significant differences. Lieberman et al found that infants in the epidural
group were less responsive to the human voice, Murray et al found that epidural was associated with lower
scores overall at day 1 with differences in motoric processes, response to
stress and state control. Differences remained at day 5, but not at one month.
Sepkowski et al found that epidural was associated with lower scores on
orientation and motor clusters.
o
In
6 studies that examined epidural vs. parenteral opioids: 3 found no significant
differences. Wiener found that epidural group habituated to sound more quickly
and had poorer muscle tone. In another study, Wiener found epidural group had
decreased reflexes and poorer muscle tone. Kangas-Saarela found epidural
infants habituated to sound and oriented to inanimate sound better.
(Lieberman) Sample sizes were small.
·
Effects on
breastfeeding.
2 studies: Kiehl found women who had received epidural were less likely to be
breastfeeding at 6 months (30% vs. 50%). Halpern found that the drugs used in
labor did not predict difficulty in initiating breastfeeding or level of
breastfeeding at 6 to 8 weeks postpartum. However, there are issues with both
study designs which make these results difficult to interpret. (Lieberman)
Research
Evaluations of Care Recommendations for Minimizing Side Effects of Epidurals
Coping with the
Diminished Urge to Push: Directed pushing vs. Laboring Down. Common management is
directed, strong, sustained pushing efforts with prolonged breath holding.
“There is no research to support the necessity of this practice.” (Mayberry)
This approach carries some risk for fetal compromise because of decreased
oxygen, risk of increased maternal fatigue, and risk of short- and long-term
pelvic damage.
Another
option is ‘delayed pushing’ or ‘laboring down’. The woman simply allows the
baby to descend on its own, not beginning active pushing until the baby’s head
is crowning, and/or she feels the urge to push. Recent studies show no adverse
fetal effects of delayed pushing for up to three hours, plus a reduced risk of
instrumental or cesarean delivery. There may be an increase of fever with
delayed pushing. (cited in Mayberry)
Timing of epidural /
Delaying epidural administration to reduce side effects:
·
Impact on risk of
cesarean: All
9 studies examining the association of epidural timing with cesarean delivery
among nulliparous women reported a higher rate of cesarean with earlier
epidural. Most studies reported relative risks between 1.6 and 2.2, although
not all the differences were statistically significant. Thorp examined the
effect of labor characteristics on this: For slow dilators (< 1 cm/hr in
early labor), epidural before 5 cm dilation was associated with a higher risk
of cesarean delivery than late epidural (24% vs. 7%). However, for fast
dilators (≥ 1 cm/hr in early labor), the timing of the epidural made no
statistically significant difference in the rate of cesarean delivery (14%
early epidural vs. 11% late epidural)
·
Instrumental
delivery: Data
suggest that there’s a modest increase in the chance of instrumental vaginal
delivery for early epidural.
·
Progress of labor: Thorp found a
longer length labor for slow dilators with early epidural rather than late, but
no difference for women who dilated quickly in early labor. Robinson et al
found no significant difference in the length of second stage for early and
late epidurals, Sheiner reported shorter early labors among women who received early
epidurals, but the difference was not statistically significant. The
inconsistent findings may be caused by several confounding factors.
·
Fetal malposition: Robinson found
malpositioning amongst nulliparas to be 32% with early epidural and 12% with
later epidurals, for multiparas 16% vs. 3%. Sheiner found no statistical
difference between early and late epidural. (Lieberman)
·
Fever. Because the risk of
fever, and the severity of fever increase with duration of epidural, the less
time spent with epidural, the lower chance for fever.
“Light” versus
“standard” epidural:
4 RCT’s. No significant differences in the proportion of women with
instrumental vaginal or cesarean delivery, or length of labor, or fetal
outcome. First stage labor was consistently longer with “light” epidural.
(Lieberman)
Intermittent versus
continuous infusion.
1 observational study and 6 RCT’s. Little evidence for large differences in
maternal or infant outcome based on the use intermittent or continuous
infusion. (Lieberman)
Turning down the
epidural in second stage: 6 RCT’s, showing various results (see Lieberman for
full comments on issues of concern with each study). Chestnut et al found that
when epidural anesthesia was stopped at 8 cm, there was no difference in rate
of cesarean – 13% in each group; but there was a significantly higher rate of
instrumental delivery when the epidural was continued (46% vs. 24%) and second
stage was an average of 30 minutes longer (124 minutes vs. 94). There was no
significant difference in fetal malposition, fetal pH or meconium staining.
Philipsen
and Jensen’s trial included 111 women. In one group, epidural was discontinued
after 8 cm dilation. There was a 60% higher rate of c-s among women receiving
epidural (18% vs. 11%); this difference is not considered statistically
significant because of the small sample size. (cited in Lieberman)
Cool cloths to reduce
risk of fever:
An anecdotal method for reducing risk of epidural fever is to use cold
compresses on mom’s forehead or the back of her neck. I did not find research
information on this. What I did find was: a) the recommendation that tepid
water should be used rather than cold water, as cold can cause the blood
vessels in the skin to constrict, making it more difficult for heat to escape
from the body. b) information about studies of the efficacy of sponge bathing
with tepid water to reduce childhood fevers. 2 research trials found a greater
and more rapid fall in temperature after tepid sponging than after
administration of temperature-lowering drugs. One study found that
acetaminophen was more effective in rapidly lowering temperature. One found
that sponging and medication together were no more effective than medication
alone. Two studies showed that tepid sponging causes distress in children.
However, laboring women tend to greatly appreciate it. A general conclusion
could be: cool (not cold compresses) feel good for moms, and may carry an additional benefit of
reducing risk of fever. (Mahar, et al Tepid sponging to reduce temperature in
febrile children in a tropical climate. Clin Pediatr (Phila), 1994;
33(4):227-31. Aksoylar, et al Evaluation of sponging and antipyretic medication
to reduce body temperature in febrile children. Acta Paediatra Jpn, 1997;
39(2): 215-7. Agbolosu, et al. Efficacy
of tepid sponging versus paracetamol in reducing temperature in febrile
children. Ann Trop Paediatr, 1997; 17(3):283-8. Newman, J. Evaluation of
sponging to reduce body temperature in febrile children. Can Med Assoc J, 1985;
132(6):641-2.)
Sources.
Major reviews
examined:
Leighton
BL, Halpern SH.. The effects of epidural anesthesia on labor, maternal, and
neonatal outcomes: A systematic review. Am J Obstet Gynecol 2002; 186:S69-77.
Reviewed RCT’s and prospective cohort studies in which epidural anesthesia was
compared with parenteral opioids in labor. All studies were published in
English between 1980 and 2001, enrolled only healthy women with uneventful
pregnancies, and met additional criteria for quality. A total of 14 RCT that
enrolled 4324 women met their inclusion criteria. A meta-analysis was done,
combining the results of these trials to reach the conclusions presented.
Lieberman
E, O’Donoghue C. Unintended effects of epidural anesthesia during labor: A
systematic review. Am J Obstet Gynecol 2002; 186:S31-68. A total of 1900
articles were examined, and evaluated for inclusion in the review based on the
authors’ criteria. They limited their review to original reports in English, in
peer review journals since 1980; they included both randomized trials and
observational studies; they excluded studies with no control group, studies
that evaluate specific drug regimens, studies that examine epidurals for
anesthesia during cesareans, studies conducted exclusively on high-risk
populations, studies where population selection renders results uninformative,
studies with analytic choices that make results impossible to interpret, and
studies that examine outcomes only for the overall population of delivering
women.
Mayberry
LJ, Clemmens D, De A. Epidural analgesia side effects, co-interventions, and
care of women during childbirth: A systematic review. Am J Obstet Gynecol 2002;
186:S81-93. More than 700 publications were identified; they narrowed that down
to 150 studies that addressed one or more of the common side effects and
co-interventions, plus 75 articles addressing relevant clinical or nursing care
information related to unintended effects of epidurals. They only included
prospective, randomized, controlled trials published between 1990 and 2000.
These studies were then further limited by pre-established criteria: evidence
of little or no crossover effect, minimal loss of subjects after random
allocation to comparison groups, and satisfactory description of the
randomization procedures. In the final review, they included 19 studies, with a
total sample size of 2708 women.
Additional
citations:
Gonen
R, Korobochka R, Degani S, Gaitini L. Association between epidural anesthesia
and intrapartum fever. Am J Perinatol 2000; 17: 127-30.
Kannan
S, Jamison RN, Datta S. Maternal Satisfaction and pain control in women
electing natural childbirth. Reg Anesth Pain Med 2001, 26: 468-72.
Lieberman
E, Lang JM, Cohen A, D’Agostino R, Datta S, Frigoletto FD. Association of epidural anesthesia with cesarean delivery in
nulliparas. Obstet Gynecol 1996; 88: 993-1000
Philipsen
T,
Thorp
JA, Breedlove, G. Epidural Analgesia in Labor: An Evaluation of the Risks and
Benefits. Birth 23:2, 1996.
Thorp
JA, Hu DH, Albin RM, McNitt J, Meyer BA, Cohen GR, et al. The effect of
intrapartum epidural analgesia on nulliparous labor: a randomized, controlled,
prospective trial. Am J Obstet Gynecol 1993; 851-8.
Some
interesting trivia: “Women who choose epidural are more likely to be slightly
shorter, to have larger infants, and to be further along in gestation… are
admitted to the hospital earlier in labor, and dilate more slowly just after
admission compared to women who do not go on to receive epidural. The rate of
epidural use has been noted to decrease directly with greater cervical dilation
at admission.” (Sources cited in Lieberman)
*
Limitations of research data. In
reviewing research, it’s important to be aware of the limitations. For example,
if you wanted to find the increased risk of cesarean after epidural, and you
examined only one article based on one trial, that article might show anything
from a .8 relative risk (i.e. c-section was slightly less likely with epidural than without) to a 11.2 RR (c-section was
11.2 times more likely). Clearly,
this discrepancy in results requires further examination of the researcher’s methods,
sample populations, and so on.
Review
articles can give a clearer picture by examining several studies, and
commenting on strengths and weaknesses of each. However, even reviews can
suffer from an incomplete examination of the issues. Leighton and Halpern, for
example, are aware of crossover rates
and include data on them; however, when they did their meta-analysis of
all the results, they base it on “intent to treat” and don’t allow for the
substantial effect crossover has on interpreting the meaning of these results.*
Lieberman
and O’Donoghue do an excellent job of examining crossover in randomized,
controlled studies (RCT’s). A good example of the impact of this is Clark et
al. In their examination of the results by ‘intent to treat’ (examining the
results based on what group the members were assigned to), you would read that there was no difference in the
cesarean rate for women assigned to receive epidural versus opioid analgesia.
However, a stunning 52% of the
opioids group actually received
epidurals. And, of the 17 reported cesareans for dystocia in the ‘opioid
group’, 14 of those women had actually received an epidural. Thus, as Lieberman
states, “When such a high proportion of subjects do not get the treatment to
which they were assigned, the intention-to-treat analysis, though technically
correct, is impossible to interpret.”
Another
reason for the wide variation in research results (in RCT’s and in
observational studies) is that birth is a complex process, and is influenced by
many different factors which are difficult to control for or evaluate. For
example, anyone who has worked with birthing women knows that their labor
progress can be affected by psychological, social, and emotional factors. A choice
of when to use pain medication, and quite possibly what side effects are
experienced, can be influenced by such factors as different birthing
environments, labor support from spouses and family members, interaction with
medical staff, the mother’s personal history, etc. Therefore, all results
merely indicate trends in what side effects are more likely with epidural than without, and indicate what
treatments are more likely to be
effective.