Morphometric analysis of spina bifida after fetal repair shows new subtypes with associated outcomes.

objectivesThe binary classification of spina bifida lesions as myelomeningocele (with sac) or myeloschisis (without sac) belies a spectrum of morphologies. This study aimed to characterize types of spina bifida lesion and correlate them with preoperative presentation and postoperative outcome.

methodsThis was a secondary analysis of a prospective cohort of patients referred for fetal spina bifida who underwent fetoscopic repair between 2020 and 2023 at a single center. We evaluated lesion morphology on high-resolution intraoperative images and videos to categorize lesions based on placode exposure and nerve root stretching. The reproducibility of lesion classification was assessed using the Kappa statistic (κ) to measure interrater agreement between a primary and a secondary reviewer, and among two additional reviewers. Preoperative characteristics analyzed included largest ventricular diameter, tonsillar herniation level, movement of the lower extremities and lesion dimensions. Outcomes collected included duration of surgery, need for patch-based skin closure, gestational age at delivery, occurrence of preterm prelabor rupture of membranes (PPROM), length of stay in the neonatal intensive care unit (NICU) and neonatal cerebrospinal fluid (CSF) diversion.

resultsOf 60 lesions repaired during the study period, 57 had high-quality images available and were included in the analysis. We distinguished five types of lesion that differed according to the extent of nerve root stretching and neural placode exposure. The primary and secondary reviewers classified lesions with almost perfect agreement (κ = 0.854). Fetal characteristics that differed between lesion types at preoperative evaluation included lesion volume (P < 0.001), tonsillar herniation (P = 0.005) and head circumference percentile (P = 0.001). Lesion level, prevalence of talipes and movement of the lower extremities did not differ according to lesion type. Regarding surgical and perinatal outcomes, need for patch-based skin closure (P < 0.001), gestational age at delivery (P = 0.002) and length of stay in the NICU (P = 0.001) differed according to lesion type, whereas the rates of PPROM, CSF leakage at birth and CSF diversion in the NICU did not. On linear regression analysis, the severity of ventriculomegaly was associated with lesion type, but not with tonsillar herniation level.

conclusionsThere is a distinct phenotypic spectrum in open spina bifida. The severity of ventriculomegaly is associated with lesion type, rather than tonsillar herniation level. Our findings have expanded the classification of spina bifida to reveal a spectrum that warrants further study. © 2025 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.