Meconium aspiration is defined as the presence of meconium below the vocal cord and it is encountered in around 20–30% of all infants with meconium-stained amniotic fluid (MSAF) 1. Aspiration can occur in utero with fetal gasping, or after birth, with the first breaths of life. Meconium aspiration syndrome (MAS) is defined as a respiratory distress that develops shortly after birth, with radiographic evidence of aspiration pneumonitis and the presence of MSAF 2. MAS occurs in about 5% of deliveries with MSAF 3 and death occurs in about 12% of infants with MAS 4.
The presence of MSAF is observed in 12–16% of deliveries 5. In utero, the passage of meconium may simply represent the normal gastrointestinal maturation or it may indicate an acute or a chronic hypoxic event, thereby making it a warning sign of a fetal compromise. Meconium passage is rare before 34 weeks of gestation and the incidence increases steadily beyond 40 weeks of gestation 6. Factors such as placental insufficiency, maternal hypertension, pre-eclampsia, oligohydramnios, or maternal drug abuse (tobacco, cocaine) result in in-utero passage of meconium 7.
Infants born through MSAF are about 100 times more likely to develop respiratory distress than those who are born through clear fluid 8. Even in women who are at a very low risk for obstetric complications, MSAF is common and it is associated with a five-fold increase in perinatal mortality compared with low-risk patients with clear amniotic fluid 5. MAS is an important cause of morbidity and mortality in the term neonates. It accounts for 10% of all cases of respiratory failure, with a 39% mortality rate 9,10.
The approach toward the prevention of MAS in newborn has changed markedly over the last 30 years. In the late 1970s, all infants born with MSAF received upper airway suctioning before delivery of shoulders and then received tracheal intubation and suctioning. Now, suctioning of upper airway is no longer recommended, except in depressed infants, according to the American Heart Association, 2010 11.
MASF has been reported to be associated with inflammation, which is well known to initiate coagulation and impair fibrinolysis. Thrombin activatable fibrinolysis inhibitor activity (TAFIa), which is activated by thrombin, is also an inhibitor of fibrinilysis. TAFI, besides inhibiting fibrinolysis, also plays a role in the regulation of inflammation 12.This study aimed to compare meconium-stained infants who were intubated at birth and full-term infants who were subjected to oropharyngeal suction of meconium at birth in terms of mortality, MAS, respiratory symptoms, and other clinical outcome measures. This study also aimed to evaluate plasma TAFIa levels, which may be used as a sign of hypoxia or inflammation in neonates with MASF.
Patients and methods
The present study was carried out in the neonatal intensive care unit of Al-Zahraa University Hospital. It included 75 newborn infants delivered through MASF with green-stained vocal cord. The neonates studied were classified into two groups. The first group included 40 neonates with MASF who received endotracheal intubation and airway aspiration at birth; their gestational age ranged from 37 to 43 weeks and their birth weight ranged from 2.262 to 3.326 kg. The second group included 35 neonates with MASF who were subjected to oropharyngeal suction at birth; their birth weight and gestational age were matched to that of the first group.
All neonates were subjected to a full assessment of history including maternal history and delivery history, clinical examination, respiratory support after leaving the delivery room, need for ventilation and ventilation days, plain radiograph and laboratory investigations including complete blood count, kidney and liver function tests, serum blood glucose, calcium, sodium, and potassium; cord blood sample was taken to measure pH, PCO2, PO2, HCO3, an O2 saturation. A venous blood sample was drawn from all neonates six hours after birth and centrifuged for at least 20 min to measure TAFIa using a commercially available kit (TAFI activity kit; American diagnostic GmbH, Kaplaneigases, Germany). The study was approved by the local ethical committee of the national research center. Parents provided written consent for the inclusion of their children in the study.
The data collected were coded, tabulated, and analyzed statistically using the statistical package for social sciences program software version 18 (SPSS Inc., Chicago, Illinois, USA). The data analyzed were normally distributed for quantitative independent case and control variables (Shapiro–Wilk test). Descriptive statistics were calculated as mean±SD and minimum and maximum of the range. Inferential analyses were carried out using an independent t-test, whereas correlations were assessed using the Pearson correlation. The comparison of categorical variables between groups was carried out using the χ2-test; the χ2-test was used for χ2 tables. Comparison of mean±SD of more than two groups in quantitative variables was carried out using the Kruskal–Wallis analysis of variance test. The level of significance was considered at P-value less than 0.050; otherwise it was considered nonsignificant.
The present study included 75 newborn infants with green-stained vocal cords; patients were classified into two groups according to the type of resuscitation. Table 1 shows the outcome of the newborn infants studied. Twenty-six (65%) neonates in group I had MAS was, whereas 20 neonates in group II had MAS (57.14%), with no significant difference between them (P=0.486). There was no significant difference in the incidence of MAS, mortality, and the age of presenting symptoms after the initial assessment, but there was a statistically significant difference in the severity of MAS and respiratory oxygen support, which was more in the oropharyngeal suction group than in the ETT suction group, P-value less than 0.05. There was a highly statistically significant difference in days of oxygen treatment, days of mechanical ventilation, and duration of hospital stay. It was prolonged in the oropharyngeal suction group than the ETT suction group (P<0.001).
Table 2 shows a negative correlation between cord blood pH and plasma TAFIa level in neonates with the complication of MASF in both groups, but no correlation was observed neonates without complications in both groups.
Table 3 shows no significant effect of sex on the severity of the primary diagnosis in both groups, but there was a statistically significant effect of birth weight and gestational age (GA) on the severity of the primary diagnosis in the oropharyngeal suction group than the ETT group.
The effect of the delivery room data of the newborn infants on the severity of primary diagnosis is shown in Table 4. The mode of delivery had no effect on the severity of MAS in both groups. However, there was a highly significant association between poor fetal heart rate (FHR) tracing pattern and severity of MAS in both groups (P<0.001). Meconium thickness had a significant effect on the severity of MAS in the oropharyngeal suction group than the ETT group.
Poor FHR: presence of tachycardia, absence of intrapartum fetal acceleration, or presence of bradycardia.
We preferred to calculate the percentage by column to clarify the percentage of each group.
For cord blood gases and TAFIa activity, a significant difference was reported in relation to the severity of MAS, proving that MAS was associated with more acidosis, hypoxia, and depressed fibrinolysis as shown in Table 5.
Meconium aspiration affects primarily term and postmature infants, and may remain a serious cause of respiratory distress. The Egyptian Neonatal Network guide in 2010 reported that 4.2% of all deliveries develop MAS 13. Adequate airway management at birth cannot prevent meconium aspiration as meconium may be aspirated by the fetus before delivery 14. This study was carried out in neonatal intensive care unit of the El-Zahraa university hospital to study the complication of MSAF and to compare the clinical outcome between neonates who were intubated for suction of meconium and others who were subjected to oropharyngeal suction only. This study also aimed to evaluate plasma TAFIa levels in neonates with MSAF. Patients were classified into two groups: the first group included 40 neonates with MASF who received endotracheal intubation and airway aspiration at birth and the second group included 35 neonates with MASF who were subjected to oropharyngeal suction at birth. In this study, there was no significance difference between the groups studied in the incidence of MAS. It was 65% in the ETT suction group and 57.14% in the oropharyngeal suction group (P>0.05). This result was in agreement, to some extent, with Wiswell et al.15, who found no significant difference in the incidence of MAS, supporting the concept that it was not necessary to intubate vigorous infants irrespective of the nature of MASF (thin or thick). In our study, there was no significant difference between the two groups in the age of presenting respiratory symptoms; we reported that infants with late-onset respiratory distress (>4 days) tended to have a more benign course. This is possible because an inflammatory response to the inhalation of meconium will not be clinically apparent before 4 h after birth. This is in agreement with Xu et al.16, who reported that late-onset respiratory distress is usually accompanied by mild MAS. Our study found that there was a statistically significant difference in the severity of MAS and respiratory oxygen support more in the oropharyngeal suction group than in the ETT suction group (P<0.05). This is in agreement with a study carried out by Singh et al.17. In our study, there were highly statistically significant differences in days of oxygen treatment, days of mechanical ventilation, and duration of hospital stay between the two groups studied. They were prolonged in the oropharyngeal suction group than the ETT suction group (P<0.001). Also, in this study, the incidence of mortality in the oropharyngeal suction group (35%) was higher than that in the ETT suction group (11.53%), with no significant difference. This is in not in agreement with Singh et al.17, who showed that 10% of MAS infants died. These results indicate that all infants with MSAF should be intubated and suctioned to decrease the risk of respiratory complications and mortality and this was in agreement with Shaikh et al.7.
To study the role of meconium in hypoxia and inflammation, we measured the plasma TAFIa level within the first 6 h after birth. We found a negative correlation between cord blood pH and TAFIa level in the MSAF infants with the complication of MAS in both groups (P<0.001). However, no correlation was observed in nonsymptomatic MSAF infants in both groups. The same results were observed by Gursoy et al.12, who showed that plasma TAFIa levels were increased in neonates with MASF.
In terms of mode of delivery, 50.6% of the newborn infants studied were delivered by cesarean section (CS) and 49.3% were delivered by normal vaginal delivery, with no significant difference between them (P>0.05). This was in not in agreement with Shaikh et al.7, who reported a higher CS rate in MASF than that in the clear liquor group. In our study, there was a statistically significant effect of birth weight and GA on the severity of the primary diagnosis in the oropharyngeal suction group than the ETT group. This was in agreement with Kumari et al. 18, who showed that the incidence of meconium passage during labor increases with GA. This finding was also confirmed by Imelda et al.19.
In terms of patients’ delivery history, study of the data for 24 h FHR monitoring before delivery showed that normal FHR patterns were associated with a good outcome in both groups. In contrast, poor FHR patterns were associated with a significant adverse neonatal outcome in both groups. Our results were in agreement with those of Xu et al.16 who reported that abnormal FHR patterns were associated with an increased risk of perinatal mortality and morbidity.
In terms of consistency of meconium, our study showed that meconium thickness had a significant effect on the severity of MAS in the oropharyngeal suction group than the ETT group. This is in agreement with a study carried out by Bhat and Rao 20, who found that the occurrence of MAS in neonates stained with thick meconium was greater than that in neonates with thin meconium. They added that thick meconium was found to be the only risk factor for the development of MAS by multiple regression analysis.
Our study showed that cord blood pH less than or equal to 7.26 was significantly associated with an adverse outcome in both groups. Our results were in agreement with the results of the study carried out by Velaphi and Vidyasagar 21, who concluded that factors associated with the development of MAS in neonates include thick meconium, fetal acidosis, nonreassuring fetal heart tracing, and low Apgar score. Also, Vivian-Taylor et al.22, showed that several antenatal and intrapartum factors were associated with the development of MAS including CS, abnormal FHR, low Apgar score, and fetal acidosis.
There was a higher incidence and severity of MAS in the oropharyngeal group rather than the ETT group; thus, we recommend that routine suctioning of the trachea under direct vision of vigorous meconium-stained neonates should be considered to decrease the risk of developing MAS. Risk factors that are associated with the development of MAS among infants with MSAF include thick meconium, fetal acidosis, nonreassuring fetal heart tracing, and low Apgar score. Also, we found an increase in TAFIa levels in neonates with MSAF and this may indicate depressed fibrinolysis.
Conflicts of interest
There are no conflicts of interest.
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