THE SIGNIFICANCE OF MECONIUM STAINED AMNIOTIC FLUID – A CROSS SECTIONAL STUDY IN A RURAL SETUP

Background: The significance of meconium in amniotic fluid is a widely debated subject. Traditionally meconium has been viewed as a harbinger of impending or ongoing fetal compromise; however some investigators believe that it is not associated with fetal hypoxia, acidosis or fetal distress. Others have found lower Apgar scores in meconium stained neonates. Objectives: To study the correlation of meconium in amniotic fluid with perinatal outcome. Methods: 120 consecutive, term, labouring women with meconium stained amniotic fluid on spontaneous/artificial rupture of membranes were monitored during labour with fetal heart rate abnormalities, one and five minute apgar score , umbilical cord pH at birth and neonatal complications, as outcome variables. Results: . Fetal heart rate variations were more often in cases with thick meconium (86.36%) than with thin meconium (9.75%%) (p value < 0.005). Thick meconium group neonates had lower Apgar scores as compared to moderate and thin meconium group. The umbilical cord blood pH was below 7.2 in 4(11.4%) neonates of thin meconium, 15(42.85%) in moderate meconium g and 30(68.18%) in thick meconium group (P value below 0.001). Neonatal complications were found in 36.36% of thick meconium group as compared to 14.28% of moderate meconium and none in thin meconium. Conclusions: Thick meconium should suggest immediate intervention, need for skilled paediatrician at the time of delivery and intensive care in the neonatal period to give a positive outcome


Introduction
Meconium is the name given to substances which have accumulated in the fetal bowel during intrauterine life. Although 69 % of newborns pass meconium by 12 hours of age, many infants pass meconium prior to birth as well 1 . Various studies have reported an incidence of meconium stained amniotic fluid ranging from 1.5 to 18 % 2 .It has been suggested that the fetus passes meconium in response to hypoxia and that meconium therefore signals fetal compromise. Alternatively, in utero passage of meconium may represent normal gastrointestinal tract maturation under neuronal control. Meconium passage could also follow vagal stimulation from common but transient umbilical cord entrapment 3 . The significance of meconium in amniotic fluid is a widely debated subject. Traditionally meconium has been viewed as a harbinger of impending or ongoing fetal compromise; however some investigators believe that it is not associated with fetal hypoxia, acidosis or fetal distress 4 . Others have found lower Apgar scores in meconium stained neonates 4 . The predictive value of meconium was better when it occurred in high risk patients and was thick, dark and tenacious. Lightly stained meconium had a poor correlation with fetal hypoxia 5 . The moderate and thick meconium group has a significantly greater risk of an abnormal FHR tracing, a 1 and 5 minute Apgar score less than 7, a cord blood pH of less than 7.2, sepsis, need for O 2 support and level III NICU admission of babies 4 . However, many babies born with MSAF have normal umbilical artery pH, so recent literature tends to disregard the importance of intrapartum meconium as a sign of fetal hypoxia. Aspiration of the meconium into fetal or neonatal lungs is associated with clinical disease ranging from mild respiratory distress to severe respiratory compromise and causes significant increase in perinatal morbidity and mortality 6 . Thus this study was done with an objective to correlate the presence of meconium in amniotic fluid with perinatal outcome so as to know its significance as an indicator of fetal distress.

Material and Methods
The present study was carried out in the department of Obstetrics and Gynaecology of a tertiary care institute of a rural area, prospectively over a period of 8 months. 120 consecutive IJBAR (2012) 03 (12) www.ssjournals.com women who reported to the labour unit with single, intrauterine term live foetus with cephalic presentation, spontaneous onset of labour with 3 cm or more cervical dilatation and in whom there was presence of meconium in amniotic fluid on spontaneous rupture of membranes (SRM) or artificial rupture of membranes (ARM) were included in the study after proper consent. Meconium was graded as "thick " if the fluid was viscous, tenacious and contained large amount of particulate material, "thin" if fluid was normal except for greenish colouring and was considered moderate if it was thicker and darker in colour. The labour was monitored closely and the mode of delivery, Apgar scores at one and five minutes and umbilical cord blood ph at birth were recorded. The neonate was followed in the immediate postpartum period and the outcome was noted. The data was analysed with Epi Info software. Ethical clearance was obtained from institutional ethical committee.

Results
During the study period of 8 months there were 3673 births and 120 women had meconium stained amniotic fluid (3.48% Difference is statistically significant ( p value below 0.01). The one minute Apgar score was between 4-6 in 17.07% of thin meconium group, 28.57 % of moderate meconium and 47.72 % in thick meconium group. The difference was statistically significant with a p value < 0.005. One neonate (3.84%) in thin meconium group, 7 (20%) in moderate meconium group and 13 (29.54 %) in thick meconium group had 1 minute Apgar score between 0-3.( p value below 0.005). One neonate (3.84%) in thin meconium group, 5 (14.38%) in moderate meconium group and 12 (27.27%) in thick meconium group had a 5 minute Apgar score between 4-6.( P value below 0.02). None of the neonates in thin or moderate meconium group had a 5 minute Apgar score between 0-3. Only one baby (2.27%) of the thick meconium group had a 5 minute Apgar between 0-3 ( Table 2). The umbilical cord blood pH was below 7.2 in 4(11.4%) neonates of thin meconium, 15(42.85%) in moderate meconium group and 30(68.18%) in thick meconium group (P value below 0.001( Table 2). None of the babies of thin meconium group had adverse neonatal outcome. In moderate meconium group 5(14.28%) babies had neonatal complications; out of these 2 had septicaemia, 1 had hypotonia, 1 had meconium aspiration syndrome and 1 baby had neonatal seizures. Thick meconium group had 16(36.36%) babies with neonatal complications out of which 6 had meconium aspiration syndrome 2 had septicaemia 6 neonatal seizures and 2 had hypotonia. The difference was statistically significant with a P value below 0.001.There were 5 neonatal deaths in the study population ;1 in moderate meconium group and 4 in thick meconium group. The cause of death in 4 neonates was birth asphyxia with meconium aspiration syndrome and in 1 neonate cause of death was severe birth asphyxia with septicaemia.

Discussion
The detection of meconium stained amniotic fluid during labour often causes apprehension and anxiety for the health provider as it is often considered an indicator of fetal distress 7 . However the obstetric literature still has many unanswered questions regarding the significance of meconium in the amniotic fluid and the appropriate management protocols that should be followed when it is discovered. It is believed by some medical experts that the passage of meconium is triggered by fetal stress, such as hypoxia or asphyxia, and that the presence of meconium in the fluid may be considered an indicator of fetal distress. Others point out that the presence of meconium in the amniotic fluid also may be a result of gastrointestinal maturity. Normal preterm foetuses rarely pass meconium; meconium passage in term or post term pregnancies is observed more frequently. Many researchers disregard the importance of meconium stained amniotic fluid as an indicator of fetal hypoxia. However a significant association has been reported between the consistency of meconium ( thick versus thin) and abnormal fetal heart rate patterns ,increased rates of caesarean section, low Apgar scores and acidic umbilical cord pH [8][9][10][11] .
IJBAR (2012) 03 (12) www.ssjournals.com In the early 2000, the prevalence of meconium aspiration syndrome (MAS) ranged from 0.20% to 0.54% in the general population 12-14 and from 1.0% to 6.8% in infants born through meconium stained amniotic fluid (MSAF) 15 26 , however patients with MSAF need strict supervision during labour for better perinatal outcome. Starks had reported significantly lower 1 and 5 minute Apgar scores, lower scalp pH values in babies of thick meconium but no increased risks in babies of thin meconium 18 . Thick meconium as single variable appeared to be most significant factor influencing fetal outcome. In the present study the 1 minute and 5 minute Apgar scores were studied as a measure of neonatal outcome and statistically significant number of infants in moderate and thick meconium group had low Apgar scores as compared to thin group. Many researchers have reported similar findings. Naqvi reported that unsatisfactory Apgar scores were two times more common in MSAF 7 . Wong identified 29 % of MSAF versus 19 .4 % of clear fluid group had low 1 minute Apgar scores 24 . However Becker found no statistically relevant difference in the Apgar scores of the subgroups of meconium 21 . The low Apgar scores may be because of direct vasoconstrictor effect of meconium on umbilical vein that results in vasospasm leading to impaired placental blood flow 27 .
IJBAR (2012) 03 (12) www.ssjournals.com The umbilical cord blood pH was below 7. Meconium though is sterile reduces the antibacterial property of amniotic fluid by altering levels of zinc and thus facilitate intraamniotic infections. In the presence of fetal stress such as hypoxia the gasping actions of the fetus may lead to aspiration of meconium into the lungs promoting lung tissue inflammation and respiratory distress 28 .

Conclusion
We conclude that moderate and thick meconium is associated with increased operative interventions, low Apgar scores, reduced umbilical cord pH, increased risk of birth asphyxia, meconium aspiration syndrome and overall increased perinatal mortality. However, thin meconium is shown to have low risk of perinatal complications. Thus identification of women at risk for passage of meconium in utero, antenataly is important so that intrapartum surveillance of these can be improved. Once intrapartum meconium is identified in the amniotic fluid close monitoring of the fetus with CTG or clinically, becomes imperative.  (12) www.ssjournals.com