Open Journal of Obstetrics and Gynecology, 2011, 1, 42-46
doi:10.4236/ojog.2011.12009 Published Online June 2011 (http://www.SciRP.org/journal/ojog/
OJOG
).
Published Online June 2011 in SciRes. http://www.scirp.org/journal/OJOG
Perinatal outcomes associated with meconium-stained
amniotic fluid in Japanese singleton pregnancies
Misao Satomi, Yoshie Hiraizumi, Shunji Suzuki
Department of Obstetrics and Gynecology, Japanese Red Cross Katsushika Maternity Hospital, Tokyo, Japan.
Received 3 May 2011; revised 31 May 2011; accepted 9 June 2011.
ABSTRACT
Introduction: We examined the perinatal outcomes in
Japanese singleton pregnancies associated with me-
conium-stained amniotic fluid (MSAF) in relation to
gestational age at delivery. Methods: We reviewed the
obstetric records of all Japanese singleton deliveries
after 22 weeks’ gestation managed at Japanese Red
Cross Katsushika Maternity Hospital between 2002
and 2008 (n = 11,249). Results: The incidence of
MSAF in the whole singleton pregnancies was 13%.
The incidence of MSAF at preterm, term and post-
term were 9.1%, 13% and 48%, respectively. The
incidence of intrauterine fetal death, low Apgar score
and low umbilical artery pH at delivery in cases with
MSAF were significantly higher than those without
MSAF in various gestational ages at delivery. Con-
clusio n: Obstetric management should be affected by
meconium in the amniotic fluid.
Keywords: Meconium-Stained Amniotic Fluid;
Perinatal Outcome; Preterm; Term; Postterm
1. INTRODUCTION
Meconium-stained amniotic fluid (MSAF) has been re-
ported to be associated with an obstetric hazard and sig-
nificantly increase risks of adverse neonatal outcomes at
term and preterm [1-7]. Although overall risk of adverse
outcome in MSAF has been reported to be low [2],
MSAF is suggested to signify underlying acute or
chronic fetal hypoxia [1-7]. Recently, MSAF rates have
been reported to be different among races and across
gestational age [2]. For example, Balchin et al. [2] ob-
served that the incidence of MSAF in South Asian is
higher than that in whites (Crude odds ratio 3.31, 95%
confidence interval 1.3 - 8.3, p < 0.01 by x2 test); how-
ever there have not been well documented in MSAF in
Japanese populations. In this study, we examined the
perinatal outcomes in Japanese singleton pregnancies
associated with MSAF in relation to gestational age at
delivery.
2. METHODS
The protocol for this study was approved by the Ethics
Committee of the Japanese Red Cross Katsushika Ma-
ternity Hospital. In addition, informed consent concern-
ing analysis from a retrospective database was obtained
from each subject.
We reviewed the obstetric records of all Japanese sin-
gleton deliveries after 22 weeks’ gestation managed at
Japanese Red Cross Katsushika Maternity Hospital be-
tween 2002 and 2008 (n = 11,249). The gestational age
of the pregnancies were established by ultrasonographic
examination of the fetal crown-rump length at 9-11
weeks’ gestation. In all cases of intrauterine fetal death
(IUFD), survival was checked within 2 weeks before the
period of the IUFD diagnosis. The presence of MSAF
was diagnosed clinically during delivery. The character-
istics of perinatal outcomes such as IUFD, neonatal Ap-
gar score at 1 and 5 minutes and umbilical artery pH
were extracted from patient charts. In this study, the
subjects were divided into 5 groups by gestational age at
delivery as follows: those delivered at 22 - 28, 29 - 32,
33 - 36, 37 - 40 and 41 - 43 weeks’ gestation.
Cases and controls were compared by x2 test for cate-
gorical variables. Odds ratios (ORs) and 95% confidence
intervals (CIs) were also calculated. Differences with P
< 0.05 were considered significant.
3. RESULTS
Table 1 shows the incidence of MSAF in the Japanese
singleton pregnancies by gestational age at delivery. The
incidence of MSAF in the whole singleton pregnancies
was 13% (1,409/11,249). The incidence of MSAF at
preterm (22 - 36 weeks), term (37 - 41 weeks) and post-
term (42 - 43 weeks) were 9.1% (73/804, p < 0.01 vs.
term, OR 0.70, 95% CI 0.54 - 0.89), 13% (1,297/10,363)
and 48% (39/82, p < 0.01 vs. term, OR 6.34, 95% CI 4.1
- 9.8), respectively.

M. Satomi et al. / Open Journal of Obstetrics and Gynecology 1 (2011) 42-46 43
Ta ble 2 shows the incidence of MSAF in the 5 peri-
ods of deliveries in the Japanese singleton pregnancies.
As shown in Table 2, the incidence of MSAF at 33 - 36
weeks was significantly lower than that at 37 - 40 weeks
(p < 0.01), however the incidence of MSAF at 22 - 31
weeks was not different significantly from that at 37-40
weeks (p = 0.24). The incidence of MSAF at 41 - 43
weeks was significantly higher than that at 37 - 40 weeks
(p < 0.01). Therefore, there was a ‘J-shaped’ relationship
between MSAF and advancing gestational age, with a
nadir at 33 - 36 weeks’ gestation.
Table 3 shows the perinatal outcomes in the 5 periods
of deliveries in the Japanese singleton pregnancies. In
total, the incidence of IUFD, low Apgar score and low
umbilical artery pH at delivery in cases with MSAF
were significantly higher than those without MSAF (p <
0.01). The incidence of IUFD in cases with MSAF was
significantly higher than that without MSAF at 29 - 32
(p = 0.03) and 33 - 36 weeks’ gestation (p < 0.01). The
incidence of neonatal low Apgar score at 1 minute in
cases with MSAF was significantly higher than that
without MSAF at 33 - 36 (p < 0.01), 37 - 0 (p < 0.01)
and 41 - 43 weeks’ gestation (p < 0.01). The incidence of
neonatal low Apgar score at 5 minute in cases with
MSAF was significantly higher than that without MSAF
at 22 - 28 (p = 0.02), 33 - 36 (p < 0.01), 37 - 40 (p < 0.01)
and 41 - 43 weeks’ gestation (p < 0.01). In addition, the
incidence of low umbilical artery pH in cases with
MSAF was significantly higher than that without MSAF
at 22 - 28 (p = 0.02), 33 - 36 (p < 0.01), 37 - 40 (p = 0.03)
and 41 - 43 weeks’ gestation (p < 0.01).
Table 1. The incidence of msaf in the japanese singleton pregnancies by gestational age at delivery.
Gestational age at delivery (weeks) Number of delivery Meconium-stained amniotic fluid
22 7 2 (29%)
23 5 1 (20%)
24 7 1 (14%)
25 13 4 (31%)
26 11 1 (9.1%)
27 22 4 (18%)
28 25 1 (4.0%)
29 47 3 (6.4%)
30 46 6 (13%)
31 49 6 (12%)
32 87 10 (11%)
33 98 8 (8.2%)
34 155 9 (5.8%)
35 143 8 (5.6%)
36 289 9 (3.1%)
37 943 31 (3.3%)
38 1,873 127 (6.8%)
39 2,902 327 (11%)
40 2,877 484 (17%)
41 1,568 328 (21%)
42 78 37 (47%)
43 4 2 (50%)
Total 11,249 1,409 (13%)
Values are expressed as number (%). P values by Χ2 test.
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Table 2. The incidence of MSAF in the 5 periods of delivery in the Japanese singleton pregnancies.
Gestational age at delivery Number of delivery Meconium-stained amniotic fluid P-value Crude OR 95% CI
22 - 28 weeks 90 14 (16%) 0.2 1.45 0.82 - 2.6
29 - 32 weeks 229 25 (11%) 0.87 0.96 0.63 - 1.5
33 - 36 weeks 685 34 (5.2%) <0.01 0.41 0.29 - 0.58
37 - 40 weeks* 8,595 969 (11%) - 1
41 - 43 weeks 1,650 367 (22%) <0.01 2.25 2.0 - 1.6
Total 11,249 1,409 (13%)
*Reference group. Values are expressed as number (%). P values by Χ2 test. OR, odds ratio; 95% CI, 95% confidence interval; IUFD, intrauterine fetal death.
Table 3. The perinatal outcomes in the 5 periods of delivery in the Japanese singleton pregnancies.
Gestational age at delivery Meconium-stained amniotic fluidP-value Crude OR 95% CI
(-) (+)
22 - 28 weeks Total 90 14
IUFD 23 (26%) 5 (36%) 0.67 -
Live fetuses 67 9
Apgar score (1 min)
<4 13 (19%) 4 (44%) 0.09 -
<7 18 (27%) 4 (44%) 0.27 -
Apgar score (5 min)
<4 5 (7.5%) 3 (33%) 0.02 6.2 1.2 - 33
<7 13 (19%) 3 (33%) 0.34 -
UApH < 7.0 2 (3.0%) 2 (22%) 0.02 9.29 1.1 - 77
29 - 32 weeks Total 229 25
IUFD 7 (3.1%) 3 (12%) 0.03 4.32 1.0 - 17
Live fetuses 222 22
Apgar score (1 min)
<4 8 (3.6%) 2 (9.1%) 0.22 -
<7 40 (18%) 5 (23%) 0.59 -
Apgar score (5 min)
<4 3 (1.4%) 1 (4.5%) 0.26 -
<7 13 (5.9%) 2 (9.1%) 0.55 -
UApH < 7.0 2 (0.90%) 0 (0%) 0.65 -
33 - 36 weeks Total 685 34
IUFD 4 (0.58%) 2 (5.9%) <0.01 10.6 1.9 - 60
Live fetuses 681 32
Apgar score (1 min)
<4 16 (2.3%) 6 (19%) <0.01 9.59 3.5 - 27
<7 39 (5.7%) 6 (19%) <0.01 3.8 1.5 - 9.8
Apgar score (5 min)
<4 4 (0.58%) 1 (3.1%) 0.09 -
<7 15 (2.2%) 4 (13%) <0.01 6.34 2.0 - 20
UApH < 7.0 5 (0.73%) 2 (6.3%) <0.01 9.01 1.7 - 48
37 - 40 weeks Total 8,595 969
IUFD 7 (0.081%) 3 (0.31%) 0.04 3.81 1.0 - 15
Live fetuses 8,588 966
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OJOG
Apgar score (1 min)
<4 25 (0.29%) 7 (0.72%) 0.03 2.5 1.1 - 5.8
<7 68 (0.79%) 27 (2.8%) <0.01 3.6 2.3 - 5.6
Apgar score (5 min)
<4 6 (0.070%) 5 (0.52%) <0.01 7.44 2.3 - 24
<7 18 (0.21%) 6 (0.62%) 0.02 2.98 1.2 - 7.5
UApH < 7.0 11 (0.13%) 4 (0.41%) 0.03 3.24 1.0 - 10
41 - 43 weeks Total 1,650 367
IUFD 1 (0.061%) 1 (0.27%) 0.24 -
Live fetuses 1,649 366
Apgar score (1 min)
<4 3 (0.18%) 10 (2.7%) <0.01 15.4 4.2 - 56
<7 16 (0.97%) 22 (6.0%) <0.01 6.53 3.4 - 13
Apgar score (5 min)
<4 2 (0.12%) 1 (0.27%) 0.49 -
<7 3 (0.18%) 5 (1.4%) <0.01 7.6 1.8 - 32
UApH < 7.0 11 (0.67%) 8 (2.2%) <0.01 3.3 1.3 - 8.3
Total (22 - 43 weeks) Total 11,249 1,409
IUFD 42 (0.52%) 14 (0.99%) <0.01 2.68 1.5 - 4.9
Live fetuses 11,207 1,395
Apgar score (1 min)
<4 65 (0.58%) 29 (2.1%) <0.01 3.62 2.3 - 5.6
<7 181 (1.6%) 64 (4.5%) <0.01 2.91 2.2 - 3.9
Apgar score (5 min)
<4 20 (0.18%) 11 (0.78%) <0.01 4.42 2.1 - 9.2
<7 62 (0.55%) 20 (1.4%) <0.01 2.6 1.6 - 4.3
UApH < 7.0 31 (0.28%) 16 (1.1%) <0.01 4.16 2.3 - 7.6
Values are expressed as number (%). P values by Χ2 test. OR, odds ratio; 95% CI, 95% confidence interval; IUFD, intrauterine fetal death.
4. DISCUSSION
The relationship between the presence of MSAF and
increased odds for birth asphyxia and neonatal mortality
is well established in preterm, term and postterm infants
[1-7]. We also found that in the infants with MSAF, the
prevalence of IUFD and/or neonatal asphyxia (low Ap-
gar scores and/or low umbilical artery pH) was increased
compared with those without MSAF in Japanese single-
ton pregnancies in various gestational age at delivery.
Therefore, obstetric management should be affected by
meconium in the amniotic fluid in all periods of preg-
nancy beyond 22 weeks’ gestation.
In this study, there was a “J-shaped” relationship be-
tween MSAF and advancing gestational age, with a na-
dir at late-preterm (33 - 36 weeks’ gestation); because
MSAF has been suggested to be mainly associated with
fetal gastrointestinal maturity rather than hypoxia under
hormonal and neural control [1,2,6]. This ‘J-shaped’
tendency seems to be similar to some previous studies
[2,6]; however the period of nadir in this study seems to
be later than those in these previous studies. For example,
the incidence of preterm MSAF at <33 weeks observed
by Tybulewicz et al. [6] and Balchin et al. [2] were only
4.3% and 5.3%, respectively; however it was 12% in the
current study. The small sample size and/or the racial
differences may be possible reasons leading to the dif-
ferences. One of other possible reasons may be that the
current data included the cases of IUFD. In this study,
for example, the incidence of MSAF in live births at <33
weeks was 9.7%. Some serious perinatal complications
such as cerebral palsy and/or severe intraventricular
hemorrhage have been reported to be more common in
infants with preterm MSAF [5,6]. Therefore, it may be
reasonable that the incidence of MSAF increased in this
study including IUFD as serious complication, because
over half of IUFD has been reported to occur during the
premature period [8]. Otherwise, very premature deliv-
ery itself can be indicated as “serious complication”
equivalent to IUFD. Therefore, further prospective ex-
amination may be needed to clarify the relation between

M. Satomi et al. / Open Journal of Obstetrics and Gynecology 1 (2011) 42-46 46
MSAF and perinatal outcomes at very preterm.
At 41 - 43 weeks’ gestation, on the other hand, the in-
cidence of low Apgar score and low umbilical artery pH
in cases with MSAF were also significantly higher than
those without MSAF. Postterm gestation itself has been
suggested to be associated with the increased risk of
perinatal mortality [9]. The higher rate of perinatal mor-
bidity at postterm gestation may be due to hypoxia/
acidemia associated with “relative placental insuffi-
ciency” where the placenta can no longer keep up the
demands of the fetus [10]. These conditions may be also
associated with the presence of MSAF. In addition, when
MSAF is superimposed on fetal acidemia, there is an
increased risk of meconium aspiration syndrome [4].
Therefore, the greater risk of adverse neonatal outcomes
at ≥41 weeks in the current study support these previous
suggestions especially in cases with MSAF [4,10].
In conclusion, obstetric management should be af-
fected by meconium in the amniotic fluid in various
gestational ages at delivery. Therefore, management re-
quires awareness of this potential risk, appropriate in-
trapartum care and a combined obstetric-neonatal ap-
proach in cases with MSAF.
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