Perinatal outcomes associated with meconium-stained amniotic fluid in Japanese singleton pregnancies

doi:10.4236/ojog.2011.12009

Paper Menu >>

Journal Menu >>

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.

Email: [email protected]

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.

M. Satomi et al. / Open Journal of Obstetrics and Gynecology 1 (2011) 42-46

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

M. Satomi et al. / Open Journal of Obstetrics and Gynecology 1 (2011) 42-46

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

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.

REFERENCES

[1] Ash, A.K. (2000) Managing patients with meconium-

stained amniotic fluid. Hospital Medicine, 61, 844-848.

[2] Balchin, I., Whittaker, J.C., Lamont, R.F. and Steer, P.J.

(2011) Maternal and fetal characteristics associated with

meconium-stained amniotic fluid. Obstetrics & Gyne-

cology, 117, 828-835.

doi:10.1097/AOG.0b013e3182117a26

[3] Natah, L., Leveno, K.J., Carmody III, T.J., Kelly, M.A.

and Sherman, M.L. (1994) Meconium: A 1990s perspec-

tive on an old obstetric hazard. Obstetrics & Gynecology,

83, 329-332.

[4] Ramin, K.D., Leveno, K.J., Kelly, M.A. and Carmody,

T.J. (1996) Amniotic fluid meconium: A fetal environ-

mental hazard. Obstetrics & Gynecology, 87, 181-184.

doi:10.1016/0029-7844(95)00403-3

[5] Spinillo, A., Fazzi, E., Capuzzo, E., Stronati, M., Piazzi,

G. and Ferrari, A. (1997) Meconium-stained amniotic

fluid and risk for cerebral palsy in preterm infants. Ob-

stetrics & Gynecology, 90, 519-523.

doi:10.1016/S0029-7844(97)00308-6

[6] Tybulewicz, A.T., Clegg, S.K., Fonfe, G.J. and Stenson,

B.J. (2004) Preterm meconium staining of the amniotic

fluid: associated findings and risk of adverse clinical

outcome. Archives of Disease in Childhood—Fetal &

Neonatal Edition, 89, F328-F330.

doi:10.1136/adc.2002.021949

[7] Ziadeh, S.M. and Sunna, E. (2000) Obstetric and perina-

tal outcome of pregnancies with term labour and me-

conium-stained amniotic fluid. Archives of Gynecology

and Obstetrics, 264, 84-87.

doi:10.1007/s004040000088

[8] Gardosi, J., Mul, T., Mongelli, M. and Fagan, D. (1998)

Analysis of birthweight and gestational age in antepar-

tum stillbirths. British Journal of Obstetrics and Gyne-

cology, 105, 524-530.

doi:10.1111/j.1471-0528.1998.tb10153.x

[9] Suzuki, S. (2009) Post-term pregnancy as a risk factor for

intrapartum fetal distress. Journal of Perinatal Medicine,

37, 420-421. doi:10.1515/JPM.2009.055

[10] Volherr, H. (1975) Placental insufficiency in relation to

postterm pregnancy and fetal postmaturity: Evaluation of

fetoplacental function; management of the postterm gra-

vida. American Journal of Obstetrics & Gynecology, 123,

67-103.