Does a myelomeningocele sac compared to no sac result in decreased postnatal leg function following maternal fetal surgery for spina bifida aperta?

Objective: A fetus with large sac S1 myelomeningocele (MMC) but bilateral talipes prompted the question, 'Does the presence or size of an MMC sac affect postnatal leg function?' Study Design: An MMC database with prenatal, birth, and a minimum of 1-year follow-up evaluation was reviewed. All fetuses had in-utero MMC repair at 20 + 0 to 25 + 6 weeks at a single institution. Fifty-four fetuses had prenatal evaluation, with 48 children completing a birth and a 1-year evaluation of leg function. Results: An MMC sac was present in 38/54 (70%) of fetuses evaluated in-utero and had been present in 35/48 (73%) of children evaluated at 1 year of age. Although leg function evaluated at 1 year was better than expected in the 'no sac' group (p = 0.059), this did not reach statistical significance. Conclusion: The presence of an MMC sac may increase postnatal lower limb morbidity.