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Frequency of meconium stained liquor in low risk laboring women and its effect on perinatal outcome in a tertiary care hospital.

… Objective: To evaluate the frequency of meconium stained liquor (MSL) in low risk women and its effect on perinatal outcomes. Study Design: Prospective Case Control study. Setting: Department of Obstetrics and Gynecology Military Hospital, Rawalpindi. Period: January to August 2017. Material & Methods: Distribution of MSL was studied according to its grade. Data included demographic profile, mode of delivery, intrapartum factors and neonatal outcomes. Descriptive statistics and chi-square were used for analysis. Results: Frequency of MSL was 376 (3.65%) among 10,281 deliveries during study period. A total of 752 women were included in the study which were divided into cases and controls. Nulliparity and advanced gestational age were significantly associated with MSL. Distribution of grade of meconium was 20.5%, 56.4% and 23.1% for grade I, II and III MSL. Breech presentation, fetal heart rate abnormalities and cesarean section were significantly associated with MSL. Low apgar score at 1 and 5 minutes, Neonatal intensive unit care admissions and fetal complications had positive correlation with MSL. Frequency of meconium aspiration syndrome (MAS) was 16.4%, birth asphyxia 5.31% and respiratory distress syndrome (RDS) 1.32% amongst all the cases of MSL. However, frequency of MAS, birth asphyxia and RDS was 0.6%, 0.19%, 0.02% in general obstetric population. Neonatal mortality was 29% in MAS, 3.4% in MSL and 0.12% in general population. Adverse neonatal outcomes had positive correlation with increasing grade of meconium. Conclusion: There is a significant frequency of meconium stained liquor even in low risk women. MSL is significantly associated with increased cesarean section rates and adverse neonatal outcomes.


INTRODUCTION
The word "Meconium" has been taken from Greek word which was used for addictive materials as meconium leads to fetal quiescence during antenatal or intrapartum period. Meconium is secreted by digestive tract which consists of mucus, cellular debris and various secretions of gastrointestinal tract. 1 The meconium stained liquor (MSL) complicates 12-16% of all pregnancies. 2 Various risk factors for MSL have been identified which includes nulliparity, hypertensive disorders of pregnancy, reduced liquor, placental pathologies, intrauterine infection, maternal intake of addictive substances and postdates pregnancy. The main causes of MSL are maturity of fetal digestive system and fetal hypoxia. 3 MSL has been well studied for its association with pathological cardiotocography, instrumental vaginal deliveries (IVD), cesarean section (CS), neonatal resuscitation, admissions to neonatal intensive care unit (NICU) due to respiratory distress syndrome (RDS), meconium aspiration syndrome (MAS), birth asphyxia and early neonatal death (ENND). 3,4 Meconium acts by blocking air passages, reduces surfactant by damaging alveoli and causes local inflammation & hypoxia. 5 The most frequent complication of MSL is MAS. https://doi.org/10.29309/TPMJ/2021. 28.07.5194 A recent study conducted by Choi W et al over the period of 6 years, found that incidence of MAS was 10.6% in cases of MSL. Distribution of mild, moderate and severe MAS was 81.7%, 5.6% and 12.7% amongst all the cases of MAS. 6 Back in 2000, the reported prevalence of MAS was 0.20% to 0.54% in all deliveries and 1% to 6.8% in deliveries with MSL. 7 Literature from 1990 to 1998 has reported a mortality of 4.6% from MAS. 8 During period of 1995-2001, a national study in United States highlighted that MAS has positive correlation with advancing gestation, from 0.10% at 37 weeks to 0.31% at 41 weeks. 9 MAS can be prevented by expediting delivery along with continuous fetal heart rate monitoring once MSL is diagnosed and by endotracheal suctioning of the neonate immediately after birth. The cause of mortality in MAS is respiratory failure due to pulmonary hypertension. Various treatment modalities for neonates with MAS are available which includes mechanical ventilation to prevent from respiratory failure, nitric oxide for better oxygenation and surfactant. These treatment modalities are very expensive and not easily accessible in all the centres. 10 Though there is lack of facility of fetal blood sampling in developing countries like Pakistan but the availability of cardiotocography (CTG) for fetal heart rate monitoring has improved neonatal outcomes. Considering MSL to be a very common problem encountered in labour ward and its association with neonatal morbidity and mortality, this study was conducted to evaluate the frequency of MSL in low risk women and its effect on perinatal outcomes in a setup where facilities for monitoring of fetal heart rate are available and deliveries are conducted by trained birth attendants and, where all the neonates with MSL are attended by pediatricians. The characteristic feature of this study was that all the women with known risk factors for MSL like maternal hypertension/renal//autoimmune disease/obstetrics cholestatsis etc and known fetal anomalies were excluded so as to find the frequency of MSL in extremely low risk women. It is generally thought that isolated MSL is a sign of fetal gut maturity with minimal association with fetal comprise. 8 We wanted to investigate this sub group of MSL.

MATERIAL & METHODS
After taking ethical approval from hospital's ethics committee, this prospective observational study was conducted in the department of Obstetrics and Gynaecology Military hospital, Rawalpindi between 1 st Jan to 31 st Aug, 2017 over the period of 8 months. All the deliveries with meconium stained liquor (MSL) served as cases. Cases were compared with random group matched with same gestational age from deliveries conducted on the same day with clear liqour. Exclusion criteria was previous cesarean section, any maternal risk factors for example diabetes/hypertension/renal/ cardiac/autoimmune disease etc, known fetal anomalies which were confirmed on 18-22 weeks anomaly scan. Distribution of MSL was studied according to its grade. Grade I MSL; watery and light yellow green, grade II MSL; watery but deep green and MSL III as thick dark green like spinach soup. A researcher trainee approached all the patients who fulfilled the inclusion criteria and after explaining objectives of the study, a verbal informed consent was taken. Data included demographic profile [age, parity, gestational age (GA)], mode of delivery [spontaneous vaginal delivery (SVD), IVD, emergency lower segment cesarean section (Em.LSCS) or elective lower segment cesarean section (El.LSCS)], intrapartum factors [induced versus spontaneous labour, cephalic versus breech presentation, duration of rupture of membranes, CTG] and neonatal outcomes [apgar score at 1 and 5 minutes, birth weight, NICU admissions, any fetal complications like MAS, birth asphyxia, RDS and ENDD]. All the information was entered on predesigned questionnaire proforma. Decision of mode of delivery was taken by senior obstetrician once MSL was found after artificial rupture of membranes (ARM). CTG trace was taken for initial 10 minutes for all the babies who were diagnosed with MSL after ARM. Then fetal heart rate was monitored by intermittent auscultation till delivery for those getting delivered vaginally. Those delivered by El.LSCS and MSL was found incidentally, their last CTG trace before LSCS was entered in proforma. Pediatrician was called at the time of delivery for babies delivered with MSL. All the babies with MSL were shifted to NICU for observation for at least 6 hours, and admitted if required. The final diagnosis of any neonatal complications was made by senior pediatrician.
Data were stored and analyzed using statistical package for social sciences (SPSS) version 23.0. Count and percentages were computed for demographic profile, frequency of meconium and its distribution according to grade, intrapartum factors and neonatal outcomes. Pearson chisquare test was used to analyse the association of various parameters with meconium and its grade. P-value less than 0.05 were considered statistically significant.

RESULTS
Total number of deliveries conducted during the study period were 10,281. Frequency of MSL was 376 (3.65%).
A total of 752 women were included in the study. Out of which, 376 women in MSL group were compared with 376 randomly selected controls, matched with gestational age.
Demographic profile of the study participants is shown (Table-I). In brief, more than seventy percent participants belonged to a age group of 20-30 years. Nulliparity predominated in MSL and had significant association with it. Many participants had a gestational age (GA) more than 39 weeks.
Majority of the cases had grade II MSL, followed by grade III and grade I as shown (Figure-1).
Fetal presentation was cephalic in more than ninety percent of the participants in both groups. However, breech presentation was predominating in MSL. Type of labour (spontaneous versus induced), duration of rupture of membranes and total duration of labour had no correlation with MSL (P>0.05). Suspicious and pathological CTG was seen more in MSL (P<0.05). More than half of the participants delivered via Em.LSCS in MSL group and it had significant association with operative delivery (Table-II).
Low apgar score at 1 and 5 minutes, NICU admissions, fetal complications in the form of MAS, birth asphyxia, RDS and ENND had positive correlation with MSL. Frequency of MAS was 16.4%, birth asphyxia 5.31% and RDS 1.32% amongst all the cases of MSL. However in general obstetric population, frequency of MAS was 0.6%, birth asphyxia 0.19%, RDS 0.02%. Birth weight was not associated with MSL. Neonatal mortality was 29% in MAS, 3.4% in MSL and 0.12% in general obstetric population (Table-III).
Neonatal outcomes according to grade of meconium are shown (Table-IV). In brief, Apgar score at 1 minute had inverse relationship with grade of meconium (P<0.01). At 5 minutes, apgar score improved in all the neonates with grade I MSL while few had low apgar score in grade II and III MSL (P=0.01). Bith weight had no association with MSL (P=0.15). Fetal complications were more in grade II and III MSL as compared to grade I MSL (P<0.05). None of the ENND were seen in grade I MSL. However with increasing grade of MSL, number of ENND increased (P<0.01)

DISCUSSION
Presence of meconium in liqour is a cause of concern for healthcare professionals because of its association with fetal distress, though it also reflects fetal maturity. 11 It is generally believed that MSL is associated with adverse perinatal outcomes.
The present study conducted on 10,281 deliveries has revealed that the frequency of MSL was 3.65% after excluding all the high risk factors for MSL, which is comparable to other studies.    years. 17 According to Rao KS et al, nulliparity is significantly associated with MSL 18 which is in line with our results. Published literature has revealed that incidence of MSL increases with advancing gestational age due to maturity of the fetal digestive system. 19 Similar results were found in our study as majority of the participants with MSL had GA more than 39 weeks.
Dordević M et al conducted a study on 282 breech deliveries and highlighted a significant association of MSL with breech presentation which is analogous to our results. 20 Though cardiotocography is considered indeterminate, our study has shown that suspicious and pathological cardiotocography was seen more in MSL (55.5%) as compared to clear liquor (17.6%). Similarly, de Souza A et al and Frey HA et al have also found significant association of meconium with abnormalities in fetal heart rate pattern which causes increased neonatal morbidity. 21,22 The present study has found no correlation of MSL with type of labour (spontaneous versus induced). This is in contrast to the Cochrane database review which highlighted increased meconium staining in induced labors (with oral misoprostol). 23 This may be because in our study almost all the participants were induced with PGE2 instead of misoprostol. This could account for variance in findings. The association of duration of labour with MSL is conflicting. Sori DM et al found no correlation of MSL with duration of labour, which mirrored the results of our study. However, Lee KA et al conducted a study on 4376 women and highlighted that higher frequency of MSL was associated with prolonged duration of labour (1 st , 2 nd stage and total as well) and with increased duration of rupture of membranes. 24 In contrast to these results, our study didn't show any association of MSL with duration of rupture of membranes. This needs to be evaluated in further studies with adjustment of confounding factors. Akin to other studies, Em.LSCS was the predominant mode to expedite delivery in our study. 13,15,24,25 Our study has strengthened the results of previous studies that MSL is one of the important factors for depressed apgar scores. 13,15,25,26,27 Similar to other studies, birth weight had no correlation with MSL. Higher NICU admissions in present study are in agreement with other studies. 16,26,28 Frequency of MAS was 16.4%, birth asphyxia 5.31%, RDS 1.32% in our study. Rao KS et al found similar rates of MAS (12%) but more cases of birth asphyxia were seen in his study (21%). 18 In a retrospective population based study by Fischer C et al, incidence of MAS ranged from 0.11% at 37 weeks to 0.49% at 42+ weeks in general population which is comparable to our results (0.6%). 12 A local data of two studies from Lahore highlighted a high mortality rate with MAS (29% and 32%) which is parallel to our results (29%). However, studies from developed countries has shown decreased neonatal mortality associated with MAS (7.9%) which may be because of one to one care and advanced treatment modalities. 12,29,30 Depressed apgar scores at 1 and 5 minutes and neonatal complications including ENND had positive correlation was increasing grade of MSL which is in accordance with other studies. 16,31 Similarly, Kumari R et al in her study on 75 patients with MSL demonstrated poor neonatal outcomes with thick meconium. 32 Despite limitations of non-availability of fetal scalp blood sampling, our study is strengthened by its large sample size, monitoring of fetal heart rate till delivery in all MSL cases, delivery by trained birth attendants, presence of pediatrician for endotracheal suctioning at birth and availability of mechanical ventilation in NICU. Moreover, a thorough association of various neonatal parameters has been evaluated with meconium in women with no known risk factors for MSL and this study has helped in predicting severity of neonatal outcomes according to grades of meconium.

CONCLUSION
Our study has highlighted that frequency of MSL is higher in even those women who had no risk factors for MSL. MSL is significantly associated with increased cesarean section rates and poor neonatal outcomes. Once meconium is detected, increased fetal surveillance, early delivery and neonatal expertise for endotracheal suctioning and ventilatory support (if required) can improve neonatal outcomes. Copyright©