What Is Meconium Ileus in Babies?

Medically Reviewed By Carla Prophete, MPAS, PA-C
Was this helpful?

Meconium ileus (MI) is a blockage of stool in the small intestine that occurs shortly after birth. It is often a first sign of cystic fibrosis (CF). When MI occurs, a baby’s first stool does not pass when it typically should. The stool may also be thicker, stickier, and drier than usual.

MI is a serious condition in newborns that requires urgent treatment to prevent complications. Keep reading to learn about symptoms and causes of MI, how doctors diagnose the condition, and options for treatment.

What is meconium ileus?

Mother in hospital bed with newborn baby lying on chest
Albert Martinez/Stocksy United

MI is a condition in which the first stool a baby produces, called meconium, cannot pass as usual due to a blockage in the small intestine.

Meconium consists of amniotic fluid, mucus, fine hair, bile, and shedding skin cells. It typically appears green, brown, or yellow.

Healthy babies produce meconium within 24–48 hours after birth. However, sometimes this stool has a viscous consistency that makes it difficult for your baby to pass. If your baby does not pass its meconium within 48 hours, it could be a sign your baby has MI. 

MI requires prompt medical care. If left untreated, it could lead to bowel perforation, which is the loss of continuity of the bowel wall. Healthcare professionals can treat a bowel perforation by surgically creating a stoma. 

Simple vs. complex meconium ileus

MI takes on two forms: simple MI and complex MI.

Simple MI occurs when thick meconium blocks the part of the small intestine that connects to the large intestine. The portion of the small intestine near the blockage dilates and fills with additional meconium, gas, and fluid. 

In complex MI, the enlarged portion of the small intestine causes complications. Babies with complex MI may experience: 

  • prenatal volvulus, which occurs when the intestines twist
  • ischemic necrosis, which involves a loss of blood flow to bone tissue
  • intestinal atresia, which occurs when the intestines do not form correctly 
  • Intestinal tearing, which causes the meconium to leak into the membrane that lines the cavity of the abdomen

Simple and complex MI occur with similar frequency in babies with cystic fibrosis.

What causes meconium ileus?

MI most often links to CF. It is typically the first sign of CF in a baby.

Cystic fibrosis

CF is a condition that makes the body’s mucus thicker, drier, and sticker. Many parts of the body utilize mucus, including the intestines. 

In newborns with CF, this thickening of mucus in the small intestine can make it difficult for meconium to pass, resulting in a blockage.

Meconium ileus and cystic fibrosis

A 2017 research review showed that MI occurs in around 20% of newborns with CF.

Among babies born with MI, 80–90% receive a diagnosis of CF.

Other causes

In rare cases, MI can occur in newborns without CF. A 2019 case report discussed genetic mutations that may cause MI.

A small 1992 study also identified MI in premature newborns who did not have CF. However, there has not been more recent research to confirm this association.

What are the symptoms of meconium ileus?

If doctors do not to detect MI during pregnancy through an ultrasound, the most common first sign is intestinal obstruction. An infant’s intestinal obstruction involves a blockage that prevents formula or breast milk from passing through the digestive tract. 

The symptoms of MI can appear within hours after birth and include: 

  • a swollen belly
  • green vomit
  • no meconium passing
  • fussiness 
  • abdominal tenderness
  • a fever of 100.4°F (38°C) or higher

How do doctors diagnose meconium ileus?

Doctors may diagnose MI during pregnancy through prenatal testing. If signs of MI present after birth, doctors can perform tests to confirm a diagnosis of MI.

Prenatal screening

Doctors sometimes detect MI prenatally through an ultrasound. Obstetricians will typically screen for MI if there is a family history of CF or if routine newborn screening tests suggest evidence of CF. 

The American College of Obstetrics and Gynecology recommends that anyone who can become pregnant receive the option of prenatal CF carrier screening as a routine part of their obstetric care.

Postnatal diagnosis

Medical professionals can diagnose MI after birth when a baby displays signs.

A doctor usually begins the diagnosis process by feeling for enlarged loops of the small bowel through the abdominal wall. To confirm the diagnosis, doctors use abdominal X-rays and contrast enemas, which create images of the intestines and reveal blockages.  

Abdominal X-rays in babies with MI reveal enlarged loops of the small intestine. Contrast enemas in newborns with MI show a blockage near the end of the small intestine and a narrower colon than usual. 

If a newborn has MI, doctors will also test for CF.

What are treatments for meconium ileus?

If an abdominal X-ray shows damage to the baby’s small intestine, such as twisting or tears, emergency surgery is necessary.

In other cases, an enema is a first-line treatment for MI. An enema is the injection of fluids into the lower bowel to clear blockages. This enema may contain N-acetylcysteine, which is a medication that can soften the thick meconium. 

If the enema does not resolve the issue, surgical removal of the MI is the next step. This process involves cutting open the intestine and removing the meconium. After successful removal, the baby’s narrow colon widens to a typical diameter. 

What is the outlook for babies with meconium ileus?

The outlook for both simple and complex MI has improved thanks to advancements in surgical and nonsurgical treatment, nutritional support, and treatment for bacterial infections. 

Without treatment, MI can lead to dangerous, potentially life threatening complications. Notify your obstetrician or care team right away if your baby does not pass meconium as they typically should.

If your baby receives a CF diagnosis, your doctor will discuss their treatment options and individual outlook with the condition.

Other frequently asked questions

These are some other questions people often ask about MI. Carla Prophete, MPAS, PA-C, reviewed the answers.

Is meconium ileus an emergency?

Meconium ileus is life threatening without treatment. Complex MI cases require emergency surgery. Simple MI cases that do not respond to an enema also require surgery. 

How soon after birth should a baby pass meconium?

Healthy babies usually pass meconium within 24–48 hours after birth. Babies with CF and premature infants may pass meconium later and require treatment for MI. 

What happens if a baby does not pass meconium?

If a baby does not pass meconium within 48 hours, a blockage in their small intestine can cause bloating and discomfort. The blockage can cause damage to your baby’s small intestine. If the intestine tears, the meconium can cause an infection and lead to shock. 


MI occurs when a blockage in the small intestine prevents a baby from passing their first stools, called meconium.

MI is most common in babies with CF. CF causes mucus in the small intestine to be thicker and stickier than usual, which can prevent meconium from passing.

Symptoms of MI can occur within hours after birth and include bloating, fussiness, and no meconium passing in 48 hours. Your OB-GYN may also diagnose MI through prenatal ultrasound.

MI requires emergency treatment to prevent life threatening complications. Doctors use enemas as a first-line treatment if there is no damage to the infant’s small intestine. Surgery is necessary if the enema does not remove the blockage or if complications occur.

Was this helpful?
Medical Reviewer: Carla Prophete, MPAS, PA-C
Last Review Date: 2022 Sep 23
View All Children's Health Articles
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Cochran, W. J. (2021). Meconium ileus. https://www.merckmanuals.com/professional/pediatrics/gastrointestinal-disorders-in-neonates-and-infants/meconium-ileus
  2. Cystic fibrosis: Prenatal screening and diagnosis. (2020). https://www.acog.org/womens-health/faqs/cystic-fibrosis-prenatal-screening-and-diagnosis
  3. Fakhoury, K., et al. (1992). Meconium ileus in the absence of cystic fibrosis. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1590459/pdf/archdisch00887-0072.pdf
  4. Parikh, N. S., et al. (2022). Meconium ileus. https://www.ncbi.nlm.nih.gov/books/NBK537008/
  5. Sathe, M., et al. (2017). Meconium ileus in cystic fibrosis. https://www.cysticfibrosisjournal.com/article/S1569-1993(17)30809-3/fulltext
  6. Skelly, C. L., et al. (2021). Meconium. https://www.ncbi.nlm.nih.gov/books/NBK542240/
  7. Woods, J. D., et al. (2019). Non-cystic fibrosis-related meconium ileus: GUCY2C-associated disease discovered through rapid neonatal whole-exome sequencing [Abstract]. https://www.jpeds.com/article/S0022-3476(19)30442-1/fulltext