Approximately 15% of women in labor receive the diagnosis of meconium-stained amniotic fluid. Some women fear that diagnosis because they heard before that it might be dangerous for their baby. I will talk about the definition of this condition and the consequences for the baby. I will also quantify the risks for your baby so that you can have more information on this subject.
The diagnosis of meconium-stained amniotic fluid is made whenever a fetus passes a bowel movement inside of an amniotic sac (first bowel movement in a baby is called meconium).
In most cases, it is not dangerous for the baby. However, when a baby is compromised due to delivery process or other factors, the baby may start vigorous gasping respirations before delivery resulting in aspiration of the amniotic fluid mixed with meconium into the baby’s lungs. That, in turn, may cause aspiration pneumonia and other more severe complications.
Meconium stained amniotic fluid – basic information
Meconium is the name used to describe the first few stools that a baby passes after birth. These first stools are black in appearance. Once stools transition and appear more normal in color, green or yellow, they are not called any more meconium; they are just healthy bowel movements.
Meconium contains everything that a fetus swallowed and processed during “in utero” life. It contains skin cells, intestinal cells, enzymes, and many different minerals and chemicals that are needed for the fetus to function before birth.
If the contents of meconium diluted in amniotic fluid reach the baby’s lungs, it can lead to a range of respiratory problems in the baby.
It is estimated that up to 15% of pregnancies are affected by meconium-stained amniotic fluid. However, only about 5%-7% of the babies exposed to such a situation end up with breathing problems.
Passage of meconium before delivery rarely occurs before 34 weeks of gestational age. It is much more common with the advancing age of the fetus; the highest risk is for pregnancies that last beyond 41 weeks of gestational age.
Three theories are trying to explain why the fetus passes meconium in utero before birth:
- Fetus passes meconium in response to low oxygen levels in its body, and it is a sign of metabolic compromise
- It may be a regular act of gastro-intestinal maturation (baby feels it is ready for life outside of the uterus)
- Meconium passage is a result of vagal nerve stimulation from umbilical cord compression
As always, when we have several theories on something, all of them may carry some truth.
Can meconium-stained amniotic fluid be prevented?
Other than preventing post-term delivery, there are no other proven methods to decrease the incidence of the meconium-stained amniotic fluid.
All other measures are aimed at decreasing the chances of poor outcomes in the baby. We know that severely metabolically compromised babies tend to have a much higher risk of developing severe aspiration pneumonia or PPHN (see below for explanations of these two conditions). Therefore, close monitoring of labor and intervening with a Cesarean Section whenever a fetus is compromised is likely to improve neonatal outcomes.
The following measures are not helpful in the management of meconium-stained amniotic fluid:
- amnioinfusion (putting an extra amount of sterile fluid in the amniotic sac)
- suctioning of baby’s nasopharynx after head comes out but before delivering rest of the baby’s body
- intubation (putting a tube into baby’s trachea) and suctioning secretions from the baby’s lungs
Consequences for the baby
There are three scenarios possible whenever a newborn baby is exposed to meconium-stained amniotic fluid during the delivery:
- Baby will be fine – no breathing problems after birth
- Baby will develop pneumonia (baby will be mildly or moderately sick)
- Baby will develop the most severe complication called Persistent Pulmonary Hypertension (PPHN).
Some doctors use only one term to describe all respiratory problems in a newborn baby due to meconium: Meconium Aspiration Syndrome. However, dividing those conditions into two categories – in my opinion – makes more sense. PPHN occurs only in a small fraction of babies who suffer from aspiration pneumonia and often require different treatments.
Baby is healthy without any breathing problems
The majority of babies (more than 90%) born to mothers with meconium-stained amniotic fluid will be healthy and will not demonstrate any breathing problems after birth. However, some babies may appear initially fine and, within a few hours since birth, will start breathing harder, and their oxygen levels will drop.
It is prudent, to monitor all babies exposed to MSAF (meconium-stained amniotic fluid) with frequent checks by skilled personnel, or to admit them to nursery and place on the monitor for several hours to ensure healthy transition after birth.
Symptoms that we will be looking for in case the baby is getting into trouble are:
- faster breathing rates
- noisy breathing (grunting)
- retractions (sinking chest movements when baby is breathing in)
- low oxygen levels on saturation monitors
- poor skin color: pale, cyanotic or bluish
- baby not willing to eat
Meconium aspiration pneumonia (Meconium pneumonitis)
Chemicals and particles that are components of meconium, when aspirated into the lungs, create local irritation and inflammation that results in pneumonia. The baby may be born only with mild respiratory symptoms. But, quickly over the next 24-48 hours, symptoms will be getting worse due to progressing inflammatory reaction in the lungs.
Baby will be breathing very fast, hard, and will require additional oxygen to maintain proper oxygen levels. Often, the chest X-ray will show clear signs of aspiration: patchy infiltrates scattered in the lungs.
Depending on the severity of the condition, the baby will receive appropriate respiratory support using one of the following methods (in order from the gentle support to more aggressive):
- oxygen hood (special plastic box around the baby’s head into which we blow extra oxygen)
- nasal cannula (plastic tubing inserted in the baby’s nose through which we provide a flow of air with oxygen)
- nasal CPAP – special apparatus placed in baby’s nose that provides additional pressure and oxygen to support the baby’s breathing
- ventilator or breathing machine – breathing tube will be placed in the baby’s trachea, and it will be connected to the machine which will be providing artificial breaths for the baby
In addition to respiratory support, the baby with meconium aspiration pneumonia will be receiving antibiotics, IV fluids, and medications to maintain appropriate blood pressure levels if necessary.
The treatment of aspiration pneumonia will vary but will be at least 7-10 days, and sometimes even longer than that. The majority of babies with meconium aspiration pneumonia do well and recover fully without any long term consequences.
In a small number of cases, babies with meconium aspiration pneumonia also develop Persistent Pulmonary Hypertension (PPHN). It is the most severe respiratory condition that one can have as a result of meconium aspiration.
Persistent Pulmonary Hypertension (PPHN)
Without getting too much into complicated physiology of PPHN, one can say that this is a condition in which due to meconium and low oxygen levels, small arteries in the lungs constrict. Blood pressure and resistence in the lung circulation increase, and due to decreased blood flow within the lungs baby has a tough time to oxygenate its blood and tissues.
Less blood is flowing into the lungs, so less oxygen is picked up in the lungs, and less oxygen is available for all the tissues in the body.
The major problem in Persistent Pulmonary Hypotension is difficulty in maintaining appropriate oxygen levels in the baby despite providing a high concentration of supplementary oxygen for breathing.
Patients with PPHN are always very sick, with labile blood pressure. Often they need to be placed on a ventilator, treated with antibiotics, blood pressure medications, and IV fluids.
If doctors have a hard time oxygenating the baby, they can use unique treatments such as inhaled nitric oxide and ECMO.
Inhaled nitric oxide is a medication that is provided to the baby in the form of an inhaled gas via a ventilator. It causes relaxation of pulmonary blood vessels that earlier constricted and caused decreased blood flow in the lungs. Before using inhaled nitric oxide, most doctors will perform an ultrasound of the heart (Echo) to confirm the diagnosis of PPHN.
ECMO is the last resort in the treatment of meconium aspiration pneumonia and PPHN. ECMO stands for Extracorporeal Membrane Oxygenation – it is a life support machine. Essentially, it is an artificial external lung (ECMO).
Baby has to undergo surgery to insert special catheters in the large vessels, which subsequently will be connected to the ECMO machine. Baby’s blood will receive all needed oxygen in the ECMO apparatus, and the baby’s lungs will have time to rest and hopefully recover from the pathologic condition.
Despite the severity of PPHN diagnosis, the vast majority of babies recover. One study cited overall mortality in babies who developed respiratory symptoms due to meconium to be 1.2% and 5% in babies who needed ECMO as a treatment of their condition (Source).
Almost all babies with respiratory problems due to meconium aspiration will be admitted to NICU for monitoring and treatment. If you would like to learn more about professionals who work in the NICU, levels of care and types of equipment used there, I invite you to read my article here.
This article is only for general information purposes. It should not be viewed as any medical advice. There is a chance that information here may be inaccurate. It would be best if you always discussed all health-related matters with your doctor before making any decisions that may affect your health or health of your family members.