Meconium aspiration syndrome (MAS) occurs when a baby inhales or aspirates meconium during delivery. Meconium is the dark green intestinal contents produced by fetuses before birth. Factors like post-term delivery or fetal distress can cause a fetus to pass meconium into the amniotic fluid before birth. If this thick, meconium-stained fluid is then inhaled or aspirated during delivery, it can block the baby's airways and cause MAS. Treatment involves immediate suctioning and clearing of the airways after birth, as well as oxygen therapy and antibiotics if needed to treat respiratory distress and prevent infection. More severe cases may require ventilation support or other advanced treatments like

1. MECONIUM
ASPIRATION SYNDROME

2. During pregnancy, the intestinal tract of a fetus is lined with a
dark green fecal material called meconium. While in the
uterus, a number of factors can cause increased movement of
the intestines and relaxation of the anal sphincter. This results
in passage of meconium into the amniotic fluid. When this
happens, the amniotic fluid and meconium mix to form a
thick, green-stained fluid. MAS can develop if the baby gasps
or inhales during labor and delivery, causing the meconium
mixture to be aspirated into the lungs. Fetal distress and post-
term delivery are the most common reasons for meconium
aspiration to develop .

3. Definition
Meconium aspiration syndrome (MAS) also known
as neonatal aspiration of meconium is a medical
condition affecting newborn infants
Meconium aspiration syndrome (MAS) is defined as
respiratory distress in the newborn due to the
presence of meconium in the trachea. It occurs
exclusively in the immediate neonatal period.

4. Meconium is a dark green fecal material produced in the intestines of
a fetus before birth. After delivery, the newborn will pass meconium
stools for the first few days of life baby may then breath the
meconium and amniotic fluid mixture into their lungs shortly before,
during, or right after birth. This is known as meconium aspiration or
meconium aspiration syndrome (MAS)

5. Meconium is a sticky dark-green substance which contains gastrointestinal secretions, amniotic
fluid, bile acids, bile, blood, mucus, cholesterol, pancreatic secretions, lanugo, vernix
caseosa and cellular debris.[
] Meconium accumulates in the fetal gastrointestinal tract throughout the third trimester of
pregnancy and it is the first intestinal discharge released within the first 48 hours after birth.
For the meconium within the amniotic fluid to successfully cause MAS, it has to enter
the respiratory system during the period when the fluid-filled lungs transition into an air-filled
organ capable of gas exchange.

6. CAUSES
MAS may occur when your baby experiences distress. It often results when the
amount of oxygen available to the fetus is reduced. Common causes of fetal distress
include:
A pregnancy that goes past the due date (more than 40 weeks)
Difficult or long labor an infection
Other factors that promote the passage of meconium in utero include placental
insufficiency, maternal hypertension, pre-eclampsia and maternal drug use
of tobacco and cocaine

7. Meconium passage as a result of fetal distress
 It is believed that fetal distress develops into fetal hypoxia causing the fetus to
defecate meconium resulting in MSAF and then perhaps MAS.
Other stressors which causes fetal distress, and therefore meconium passage,
includes when umbilical vein oxygen saturation is below 30%.
Foetal hypoxic stress during parturition can stimulate colonic activity, by enhancing
intestinal peristalsis and relaxing the anal sphincter, which results in the passage of
meconium. Then, because of intrauterine gasping or from the first few breaths after
delivery, MAS may develop. Furthermore, aspiration of thick meconium leads to
obstruction of airways resulting in a more severe hypoxia.

8. Meconium passage as a result of fetal maturity
Although meconium is present in the gastrointestinal tract early in
development, MSAF rarely occurs before 34 weeks gestation.
Peristalsis of the fetal intestines is present as early as 8 weeks gestation and
the anal sphincter develops at about 20–22 weeks. The early control
mechanisms of the anal sphincter are not well understood, however there is
evidence that the fetus does defecate routinely into the amniotic cavity even in
the absence of distress. The presence of fetal intestinal enzymes have been
found in the amniotic fluid of women who are as early as 14–22 weeks
pregnant. Thus, suggesting there is free passage of the intestinal contents into
the amniotic fluid.

9. Motilin is found in higher concentrations in post-term than pre-term fetal
gastrointestinal tracts. Similarly, intestinal parasympathetic innervation
and myelination also increases in later gestations. Therefore, the increased
incidence of MAS in post-term pregnancies may reflect the maturation and
development of the peristalsis within the gastrointestinal tract in the newborn.

11. DIAGNOSTIC EVALUATION
Respiratory distress in an infant born through the darkly coloured
.MSAF as well as meconium obstructing the airways is usually
sufficient enough to diagnose MAS.
Additionally, newborns with MAS can have other types of respiratory
distress such as tachypnea and hypercapnia.

12. A diagnosis is made based on your newborn’s symptoms and the presence
of meconium in the amniotic fluid.
Auscultation infant’s chest with a stethoscope to detect sounds of
abnormal breathing. There are a few methods commonly used to confirm
the diagnosis:
Blood gas test to evaluate oxygen and carbon dioxide levels
Chest X-ray to see if material has entered your newborn’s lungs

14. TREATMENT
If MAS occurs, immediate treatment to remove the meconium from the upper
airway. After delivery, suction the nose, mouth, and throat.
If your baby isn’t breathing or responding well, a tube may be placed in your
newborn’s windpipe (trachea) to suction the fluid containing meconium from the
windpipe. The suctioning may then continue until no meconium is seen in the
material removed.
If your newborn still isn’t breathing or has a low heart rate, use a bag and mask to
help them breathe. This will deliver oxygen to your baby and help inflate their lungs.
After emergency treatment has been provided, your newborn may be placed in a
special care unit to observe their breathing. Additional treatment may be needed to
avoid complications of MAS. Five common treatments include:

15. Oxygen therapy to make sure there is enough oxygen in the blood
The use of a radiant warmer to help your baby maintain body
temperature
Antibiotics such as ampicillin and gentamicin to prevent or treat an
infection

16. TREATMENT
To clear the airways of meconium, tracheal suctioning can be used however,
the efficacy of this method is in question and it can cause harm.
In cases of MAS, there is a need for supplemental oxygen for at least 12 hours
in order to maintain oxygen saturation of haemoglobin at 92% or more.
The severity of respiratory distress can vary significantly between newborns
with MAS, as some require minimal or no supplemental oxygen requirement
and, in severe cases, mechanical ventilation may be needed.] The desired oxygen
saturation is between 90-95% and PaO2 may be as high as 90mmHg.

17. In cases where there is thick meconium deep within the lungs, mechanical
ventilation may be required. In extreme cases, extracorporeal membrane
oxygenation (ECMO) may be utilised in infants who fail to respond to ventilation
therapy.While on ECMO, the body can have time to absorb the meconium and for all
the associated disorders to resolve. There has been an excellent response to this
treatment, as the survival rate of MAS while on ECMO is more than 94%.
Ventilation of infants with MAS can be challenging and, as MAS can affect each
individual differently, ventilation administration may need to be customised. Some
newborns with MAS can have homogenous lung changes and others can have
inconsistent and patchy changes to their lungs. It is common for sedation and muscle
relaxants to be used to optimise ventilation and minimise the risk
of pneumothorax associated with dyssynchronous breathing.

18. Inhaled nitric oxide
Inhaled nitric oxide (iNO) acts on vascular smooth muscle causing
selective pulmonary vasodilation. This is ideal in the treatment
of PPHN as it causes vasodilation within ventilated areas of the lung
thus, decreasing the ventilation-perfusion mismatch and thereby,
improves oxygenation. Treatment utilising iNO decreases the need
for ECMO and mortality in newborns with hypoxic respiratory failure
and PPHN as a result of MAS. However, approximately 30-50% of
infants with PPHN do not respond to iNO therapy..

19. Amnioinfusion has been used when MSAF was present,
which involves a transcervical infusion of fluid during labour.
The idea was to dilute the thick meconium to reduce its
potential pathophysiology and reduce cases of MAS, since
MAS is more prevalent in cases of thick
meconium. However, there are associated risks, such
as umbilical cord prolapse and prolongation of labour. The
UK National Institute of Health and Clinical Excellence (NICE)
Guidelines recommend against the use of amnioinfusion in
women with MSAF.

20. THANK YOU