Meconium Isn't the Problem; Induction Is
-by Gail Hart
of www.midwiferyeducation.org
Meconium (mec) is not a problem- unless mec is
a symptom of severe distress. And then the problem
is the distress- not the mec. With good fetal
heart tone and a normal labor, even thick mec
is rarely a problem.
Meonium is more common in labors which are induced,
by any and all means of induction, and it's debateable
whether mec is even more common in post-dates
labors since induction is often a confounding
factor. I recently came across a study (as follows)
that looks at the liklihood of whether heavy mec
is actually a risk for meconium aspiration. It's
older, but large- it looks at almost a thousand
babies with "thick or moderate meconium".
All sorts of things were found to contribute to
the rate of mec; but only a couple babies out
of a hundred actually developed meconium aspiration
syndrome- MAS- even though the entire group had
mec (39 out of 937).
Induction was a strong link to both meconium
waters and to meconium aspiration syndrome- but
(and this surprised everyone) POSTDATES was not
found to be a factor in the babies who developed
MAS: MAS was distributed equally among all gestation
groups. MAS was correlated with thick mec primarily
when there were other risk factors present- need
for resucitation, poor heart tones, or ceserean
delivery.
Induction of labor was the strongest association
with MAS. We know that we see more mec in induced
babies, and we know we see more MAS in induced
babies. A logical guess may be that we see more
mec in post-dates babies simply because post-dates
babies are far more likely to be induced than
are 40 week babies.
This study confirms what most of us have seen:
that meconium is "rarely a problem"-
even when it is thick.
Risk factors for meconium aspiration syndrome.
Obstet Gynecol 1995 Aug;86(2):230-4
Usta IM, Mercer BM, Sibai BM. Department of Obstetrics
and Gynecology, University of Tennessee, Memphis,
USA.
OBJECTIVE: To identify potential predictors of
meconium aspiration syndrome (MAS) in pregnancies
complicated by moderate or thick meconium-stained
amniotic fluid (AF).
METHODS: In the period 1990-1993, 937 vertex
singleton pregnancies with moderate or thick meconium-stained
AF were delivered; of these, 39 neonates developed
MAS and 898 did not. The two groups were compared
retrospectively according to maternal findings,
pregnancy outcome, and neonatal complications,
using univariate analysis (P < .05 considered
significant) and stepwise multiple logistic regression
analysis to identify independent significant factors
for prediction of MAS and to calculate odds ratios
(OR) and 95% confidence intervals.
RESULTS: The two groups had a similar mean gestational
age at delivery and birth weight. They also had
similar incidences of post-dates pregnancies,
small and large for gestational age infants, and
amnioinfusion use. Univariate analysis identified
significant differences between the two groups
in 13 variables, two of which were excluded from
logistic analysis because of inadequate data.
Logistic regression analysis identified only six
variables with independent, statistically significant
effects on MAS: admission for induction with nonreassuring
fetal heart tracing (OR 6.9), need for endotracheal
intubation and suctioning below the vocal cords
(OR 4.9), 1-minute Apgar score of 4 or less (OR
3.1), present cesarean delivery (OR 3.0), and
previous cesarean delivery (OR 2.5). Cigarette
smoking was associated with a lower risk for MAS
(OR 0.07). The presence of at least one of the
five risk factors had a sensitivity of 92%, a
specificity of 56%, a positive predictive value
of 8%, and a negative predictive value of 99%
for MAS.
CONCLUSION: Considering the high negative predictive
value of the test, infants without any risk factors
will not develop MAS and thus can be safely allowed
to room with their mothers. Furthermore, this
model helps to identify infants who may benefit
from 24-hour observation and in counseling women
about the neonatal risk for developing MAS.
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