Revisiting the Implications of a Wide or Narrow Fetal Cavum Septi Pellucidi.

Objectives: To investigate short-term neonatal developmental outcomes in fetuses with an isolated wide or narrow cavum septi pellucidi (CSP) using new reference ranges.

Methods: A cross-sectional study on fetuses at 16 + 0 to 36 + 6 weeks of gestation between December 2020 and January 2022. CSP width reference ranges were constructed from low-risk pregnancies. Wide and narrow CSPs were defined as measurements above the 95th percentile and below the 5th percentile, respectively. For the primary outcome fetuses with normal neurosonograms were included. Neonatal developmental outcomes were assessed using the Survey of Well-being of Young Children (SWYC).

Results: A total of 352 fetuses were included in this study, of whom 138 were healthy and had uncomplicated neonatal outcomes. These fetuses constituted the control group and were used to construct the CSP width reference ranges. Of 185 fetuses in the neurosonography group, 9.7% had wide and 7.6% had narrow CSPs, of whom 33.3% and 22.2%, respectively, scored below the SWYC threshold for expected developmental milestones, a rate similar to that reported in the general population.

Conclusions: The presence of a prenatally isolated wide or narrow CSP does not appear to increase the risk of neonatal neurodevelopmental delay.