Establishing normal ranges for fetal and neonatal small and large intestinal lengths: results from a prospective postmortem study

OBJECTIVE: To establish reference intervals (RIs) for fetal and neonatal small and large intestinal lengths. METHODS: Linear measurements on small and large intestines were made upon postmortem examination of 131 preterm and term infants with gestational ages between 13 and 41 weeks. All cases were referred from the Eastern Ontario and Western Québec regions to a tertiary care hospital. Age and sex partitions were considered and RI limits were estimated. RESULTS: Data consisted of 72 male (54.96%) and 59 female (45.04%) fetuses and neonates with mean gestational age of 25.6 weeks. Results showed that small and large intestinal lengths increased linearly with gestational age. RIs for small intestinal length (cm) of fetuses and neonates aged 13–20 weeks were (21.1, 122.4); of those aged 21–28 weeks were (57.7, 203.8); of those aged 29–36 weeks were (83.6, 337.1); and of those aged 37–41 weeks were (132.8, 406.4). RIs for large intestinal length (cm) of fetuses and neonates from the same four age groups were (5.1, 21.4), (12.7, 39.7), (32.4, 62.4), and (29.1, 82.2). CONCLUSIONS: Establishing accurate RIs for premature and term infants has clinical relevance for pathologists performing postmortem analysis and for surgeons planning postoperative management of patients. The results of this study reaffirm that fetal small and large intestinal lengths increase linearly with gestational age irrespective of sex. Future studies should aim to further investigate the role of possible confounders on growth of fetal intestinal length, including maternal factors such as age and substance use during pregnancy.