Meconium aspiration syndrome 20452 217476272 2008-06-06T05:23:48Z Arcadian 104523 mesh {{DiseaseDisorder infobox | Name = Meconium aspiration syndrome | ICD10 = {{ICD10|P|24|0|p|20}} | ICD9 = {{ICD9|770.11}}, {{ICD9|770.12}} | ICDO = | OMIM = | MedlinePlus = 001596 | eMedicineSubj = ped | eMedicineTopic = 768 | DiseasesDB = 7907 | MeshID = D008471 | }} '''Meconium aspiration syndrome''' ('''MAS''', alternatively "Neonatal aspiration of meconium") occurs when infants take [[meconium]] into their lungs during or before delivery. Meconium is the first [[stool]] of an [[infant]], composed of materials ingested during the time the infant spends in the [[uterus]]: intestinal [[epithelial cells]], [[lanugo]], [[mucus]], [[amniotic fluid]], [[bile]], and water. Meconium is sterile, unlike later feces, and has no odor. Meconium is normally stored in the infant's intestines until after birth, but sometimes (often in response to fetal distress) it is expelled into the amniotic fluid prior to birth, or during labor. If the baby then inhales the contaminated fluid, respiratory problems may occur. ==Causes and risk factors== Meconium passage into the amniotic fluid occurs in about five to twenty percent of all births. This is more common in postdate births. Meconium aspiration syndrome develops in only 5-10 percent of these cases. Frequently, [[fetal distress]] during labor causes intestinal contractions, as well as a relaxation of the anal sphincter, which allows meconium to contaminate the amniotic fluid. Amniotic fluid is normally clear, but becomes greenish if it is tinted with meconium. If the infant inhales this mixture before, during, or after birth, it may be sucked deep into the lungs. Three main problems occur if this happens: :* the material may block the airways :* efficiency of gas exchange in the lungs is lowered :* the meconium-tainted fluid is irritating, inflaming airways and possibly leading to chemical [[pneumonia]] About a third of those infants who experience MAS require breathing assistance. ==Symptoms and signs== <!-- Unsourced image removed: [[Image:meconium_aspiration_newborn_lung_streak.jpg|right|thumb|250px|Merconium streaks in newborn chest XRay]] --> The most obvious sign that meconium may have been aspirated is the greenish appearance of the amniotic fluid. The infant's skin may be stained green if the meconium was passed a considerable amount of time before birth. Rapid or labored breathing, slow heartbeat, or low [[Apgar]] score are all signs of the syndrome. Inhalation can be confirmed by one or more tests such as using a [[stethoscope]] to listen for abnormal lung sounds, performing blood gas tests, and using chest X-rays to look for patchy or streaked areas on the lungs. Infants who have inhaled meconium develop respiratory distress--often requiring ventilatory support. Complications of MAS include [[pneumothorax]] and [[persistent pulmonary hypertension of the newborn]]. ==Prevention and Treatment== MAS is difficult to prevent. Ensuring that the infant is born before 42 weeks of gestation may lessen the risk. ''Amnioinfusion'' is a method of thinning thick meconium that has passed into the amniotic fluid. In this procedure, a tube is inserted into the uterus through the vagina, and sterile fluid is pumped in to dilute thick meconium. Recent studies have not shown a benefit from amnioinfusion. Until recently it had been recommended that the throat and nose of the baby be suctioned by the obstetrician as soon as the head is delivered. However, new studies have shown that this is not useful and the revised Neonatal Resuscitation Guidelines published by the American Academy of Pediatrics no longer recommend it. When meconium staining of the amniotic fluid is present and the baby is born depressed, it is recommended that the pediatrician suction the mouth and nose and use a [[laryngoscope]] and suction catheter to suction meconium from below the [[vocal cords]]. If the condition worsens to a point where treatments are not affecting the newborn as they should, [[extracorporeal membrane oxygenation]] (ECMO) is recommended. This is essentially a [[cardiopulmonary bypass|heart-lung machine]] used for longer than normal, i.e. during surgery. ==See also== * [[Aspiration pneumonia]] ==External links== *[http://www.emedicine.com/ped/topic768.htm eMedicine's article about meconium aspiration syndrome] {{Certain conditions originating in the perinatal period}} [[de:Mekoniumaspiration]] [[es:Síndrome de aspiración de meconio]] [[pl:Zespół aspiracji smółki]] [[Category:Pediatrics]]