To evaluate the clinical value of dynamic prenatal ultrasonography in monitoring fetal intestinal dilatation, and to analyze its correlation with neonatal small intestinal obstruction, so as to provide evidence for prenatal counseling and prognostic evaluation.

A retrospective analysis was conducted on cases in which fetal intestinal width exceeded the 97th percentile for the corresponding gestational week as identified by mid-to-late pregnancy ultrasonography. All case were managed or referred to Peking Union Medical College Hospital from January 2019 to August 2025. Ultrasonic parameters recorded included the gestational week at initial detection of intestinal dilatation, severity of dilatation, amniotic fluid volume, and presence of abdominal effusion. Postnatal outcomes were followed up and statistically analyzed.

A total of 34 cases with fetal intestinal dilatation were enrolled, of whom 22 were postnatally confirmed as neonatal small intestinal obstruction and 12 had no obstruction. Compared with the non-obstruction group, the obstruction group had an earlier gestational week at initial detection of intestinal dilatation (P=0.036) and more severe dilatation [2.64 (1.50, 5.94) mm vs 1.35 (0.62, 2.32) mm; Z=3.127, P=0.002]; moreover, intestinal dilatation was detected on at least two consecutive ultrasonographic examinations. Subgroup analysis showed that jejunal atresia was more likely than ileal atresia to present with intestinal dilatation in the second trimester (77.8% vs 12.5%, P=0.023), and was accompanied by a higher incidence of polyhydramnios (88.9% vs 12.5%, P=0.003). All 8 cases complicated by meconium peritonitis had abdominal effusion, and 3 of them showed a transient reduction of intestinal diameter. Except for one infant with ileal atresia who died after surgery, all other infants achieved a favorable prognosis.

Dynamic prenatal ultrasonic monitoring of fetal intestinal dilatation, combined with indicators including gestational week at detection, dilatation severity, amniotic fluid volume, and abdominal effusion, enables accurate prediction of fetal small intestinal obstruction and its location, as well as early identification of complications such as meconium peritonitis. This is of crucial clinical significance for prenatal prognosis assessment and genetic counseling.