Meconium is the first intestinal discharge from newborns. Newborns normally pass meconium in the first 24-48 hours. Sometimes, the infant will pass meconium while still in the uterus. Oftentimes, the passage of intrauterine meconium will be due to medical conditions like preeclampsia, uncontrolled hypertension, diabetes mellitus, postterm pregnancy and autoimmune diseases among others. Although, there are instances where intrauterine meconium will be present in a seemingly normal pregnancy. The use of tobacco and illicit drugs can also increase the chances of intrauterine meconium. Meconium is rarely found prior to 34 weeks gestation so the presence of meconium is usually at term, near term, or postterm. The exact reason for the presence of meconium is unknown.
The most concerning aspect of intrauterine meconium is the potential for meconium aspiration by the infant. In this case, the meconium travels into the infant’s lungs and can cause a pneumonia which can interfere with oxygenation. Years ago, the meconium was aspirated by the provider as soon as the head was delivered, and while the infant’s body was still in the birth canal. These days, the infant is delivered, and taken quickly to a warmer where wall suction is used to aspirate the meconium. Optimally, the wall suction aspiration is done before the infant draws a breath. Unfortunately, sometimes the meconium aspiration occurs while the infant is still in utero in which case wall suction aspiration may not help. Some of these infants will develop respiratory distress syndrome and will have to be placed on a ventilator. Fortunately, meconium is sterile and does not have bacteria. On rare occasion, meconium aspiration syndrome will be associated with persistent pulmonary hypertension of the newborn which can be life threatening.
Besides ventilation, the infants will be treated with antibiotics, a warmer, and possibly ECMO (extracorporeal membrane oxygenation). ECMO is used when the infant is not responding to other oxygen treatments. ECMO makes use of a pump and machine to do the work of the infant’s lungs so that the lungs have time to heal.
There is an increased risk of adverse outcomes for the full term infant with meconium aspiration. These include neurological problems, and acidemia (severe acidity in the bloodstream). Even though death is a possibility, this is uncommon. The chances of the meconium aspiration infants going to the neonatal intensive care unit is increased compared to those infants without meconium aspiration.
As mentioned earlier, meconium aspiration is largely found in term, near term or postterm infants. But preterm infants will occasionally have meconium in the amniotic fluid as well. These infants also have an increased incidence of bad outcomes. These include intrapartum and postpartum death along with cerebral palsy.
Examination of the placenta will reveal brown or green staining from the meconium. The placenta is examined in cases of meconium to see if an underlying cause is uncovered. But again, most cases of intrauterine meconium do not have a clear cut reason.
The presence of meconium is a relatively common occurrence. Your provider and staff will know how to deal with this issue.
Wishing you a happy and uneventful delivery, Pablo.