Meconium
Meconium is the build-up of waste products in the intestines of the fetus. It is often described as black and tarry. It starts to accumulate in the intestines at around 34 weeks' gestation. Usually, the newborn baby passes the meconium in a series of bowel movements in the first few days after birth. Around day three to five, a baby's bowel movements transition first to a dark green and then turn to yellow, seedy stools.
- Babies should have their first meconium bowel movement within the first 24 hours of life. All healthy newborns will pass meconium within the first 48 hours of life. Some babies will pass their meconium in the delivery room.
- If a baby does not have a bowel movement in the first 24 hours, a health-care provider needs to see the baby.
- If a baby does not have a bowel movement in the first 24 hours, this may be due to an illness such as hypothyroidism, cystic fibrosis, bowel obstruction (intestinal blockage) or Hirschsprung disease.
Meconium ileus
Meconium ileus occurs when meconium acts like a plug and blocks part of a baby's intestine. Babies with meconium ileus:
- do not pass meconium for the first few days
- begin to have vomiting and enlargement of their belly in the first few days
About 80 per cent to 90 per cent of babies with meconium ileus have cystic fibrosis. Any baby who has not passed stool for the first 24 hours, or a baby who is developing vomiting and distension (enlargement) of the belly in the first few days of life, needs to see a health-care provider immediately.
Meconium aspiration syndrome (MAS)
Meconium aspiration syndrome is a condition in which a baby develops problems breathing because they inhaled meconium mixed with amniotic fluid into the lungs before or during the delivery. This is most common when the baby is post-term or if the fetus experiences stress before or during birth. The newborn baby's air passages can become blocked, and their lungs can become inflamed. Meconium aspiration is a frequent problem in newborn babies and affects approximately 10 per cent of births. A small proportion of babies who aspirate meconium develop respiratory distress, or difficulty breathing. Some of these newborn babies need extra oxygen and breathing assistance with a machine to help with ventilation.
Risk factors for MAS include:
- Post-dates babies (babies born at a gestational age of more than 41 weeks)
- Small for gestational age babies (babies who have a low weight compared to what would be expected for their gestational age)
- Fetal distress and/or a difficult delivery
- Problems with the placenta or umbilical cord
The treatment for meconium aspiration depends on how severe the problem is. In newborn babies who have weak or no breathing signs, a tube may be placed immediately into the windpipe to suction meconium from beneath the vocal cords. The newborn baby may need breathing assistance with a machine to help with ventilation and oxygen. Antibiotics may be started to treat infection and pneumonia.
Meconium in the lungs tends to deactivate the fatty substance called surfactant, which is necessary for the air sacs to fill properly with air. Newborn babies with meconium aspiration may need to receive a dose of surfactant to overcome this problem.
In mild cases of meconium aspiration, the condition subsides in two to four days. The newborn baby may have episodes of rapid breathing for a few extra days. Most newborn babies recover fully from this condition, and there usually is no lung damage. Some newborn babies with severe meconium aspiration require ventilation (breathing assistance) and a longer stay in a special care nursery.
If a baby has meconium aspiration syndrome, then treatment will begin right away in the delivery room. The baby may require oxygen and/or a mask over the face to deliver pressure to keep the airways open. Further treatment may include putting a tube into the airway and suctioning out some of the meconium. The baby will need to go to the special care nursery or the neonatal intensive care unit for further tests and treatment.
Meconium peritonitis
Meconium peritonitis occurs when there is rupture of the bowel before birth (the bowel opens, and then there is a hole in the bowel). The meconium leaks out into the space that surrounds the bowels (peritoneum), and the lining of the abdomen (peritonitis) becomes inflamed.
Infants with cystic fibrosis are at increased risk for meconium peritonitis.
How is meconium peritonitis diagnosed?
- It could be diagnosed before birth if areas of calcium deposits are seen in the peritoneum on an ultrasound test.
- It could be diagnosed after birth if the baby is born with vomiting and an enlarged abdomen. On an X-ray, the bowel will be enlarged (dilated).
Why would the bowel rupture?
The bowel could rupture if there is an underlying problem, such as:
- volvulus (twisting of the bowels)
- small bowel atresia (abnormal formation of the bowels where the small bowel comes to an end instead of connecting to the rest of the large bowel)
- microcolon (an abnormally narrow lower section of bowel)
- intussusception (the bowel telescopes into itself)
- imperforate anus (the anus is not open/patent)
What will happen?
Sometimes, the bowel heals on its own prior to birth. Other times, the baby may require surgery to fix the underlying problem after birth.
A fetus with meconium peritonitis needs careful monitoring, including:
- regular ultrasounds
- follow-up with an obstetrical team and a surgical/neonatal team at a high-level (tertiary) care centre
- plan for delivery at a hospital that has a neonatal intensive care unit