meconium aspiration syndrome

Meconium is often passed by the baby before delivery, in response to the normal stresses of labor or actual fetal distress (low blood oxygen, or hypoxia). Ordinarily, this does not pose a threat to the baby's health. However, if the fetus has suffered oxygen deprivation and has begun intrauterine gasping respiratory movements, significant amounts of meconium can be sucked down into the lungs. These chunks of crud cause blockage of the bronchi (breathing tubes). This in turn causes difficulties for the baby with oxygenation of the blood, because blood flows to areas of the lung not being aerated. The other major problem is the tendency for ball-valve type obstruction of the brochial tubes.

During inspiration, the chest and everything in it expands. This includes the bronchial tubes. If a bronchial tube has a chunk of meconium lodged in it, when the chest expands during inspiration, air may be able to flow into the section of the lung served by the bronchus, but during expiration, the bronchus shrinks in diameter and cuts off the airflow out. This has the effect of pumping air into a section of the lung, which may rupture and leak air around the lung(pneumothorax). This causes collapse of the involved lung and pressure on the heart which can reduce its filling capacity and hence its pumping capacity. These bad effects can in turn lead to the development of persistent fetal circulation, further decreasing oxygenation to the baby.

For this reason, babies known in advance or discovered at delivery to have meconium staining of the amniotic fluid, especially if the meconium is chunky and particulate, will usually be suctioned out as quickly as possible after birth - before the first breath is taken is best - by an experienced doctor or nurse who will insert a tube through the vocal cords into the windpipe and suction out as much meconium as can be gotten.

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