Meconium-Related Obstruction and Clinical Outcomes in Term and Preterm Infants.

Importance: Textbooks attribute 80% of meconium-related small bowel obstructions to cystic fibrosis and 15% of colonic obstructions to Hirschsprung disease. It is unknown whether these estimates are accurate, particularly among preterm infants, whose immature bowel predisposes them to meconium-related obstruction (MRO). Objective: To estimate the incidence of MRO by type and to assess its association with clinical outcomes. Design, Setting, and Participants: This retrospective cohort study of live-born infants included in the National Inpatient Sample from January 1, 2016, to December 31, 2020, used survey weighting methods to estimate the national incidence of MRO by etiology. Data were analyzed from November 27, 2023, to November 12, 2024. Exposure: MRO. Main Outcomes and Measures: The primary outcome was diagnosis with MRO. Secondary outcomes included mortality, need for abdominal surgery, hospitalization duration, and cost. Multivariable regression models were developed to evaluate characteristics associated with MRO and to assess the association of MRO of prematurity with clinical outcomes after adjusting for demographic and clinical covariates. Results: Of 3 550 796 infants, 51.2% were male and 46.7% were privately insured. Overall, 9.1% (n = 322 499) were born preterm. Of 1844 (0.1%) infants treated for MRO, 41 (2.2%) had cystic fibrosis, 60 (3.3%) had Hirschsprung disease, and 1743 (94.5%) had neither predisposing condition. Preterm infants were at highest risk for MRO, with 4.7 MRO cases per 100 000 births associated with cystic fibrosis, 4.7 MRO cases per 100 000 births associated with Hirschsprung disease, and 187.3 MRO cases per 100 000 births associated with neither predisposing condition. Among infants with neither cystic fibrosis nor Hirschsprung disease, those with gestational ages from 28 weeks to 31 weeks 6 days were most likely to develop MRO compared with term infants (adjusted odds ratio, 6.08 [95% CI, 4.27-8.67]). Among preterm infants, having an MRO was associated with a 4.2 percentage point increase in the probability of abdominal surgery (95% CI, 3.1-5.4 percentage points), a 7.3-day increase in length of stay (95% CI, 5.8-8.8 days), and a $23 215 increase in hospitalization costs (95% CI, $17 739-$28 690) compared with infants who did not have an obstruction, with no change in mortality rate (0.1 percentage point change [95% CI, -0.6 to 0.8 percentage points]). Conclusions and Relevance: In this cohort study of over 3.5 million infants, MRO was most likely to occur among preterm infants without cystic fibrosis or Hirschsprung disease. These infants more frequently required surgery and had longer and more costly hospitalizations, indicating a need for dedicated prevention and treatment pathways for this understudied disease.