Purpose: To construct nomograms for the fetal cerebellar vermis and brainstem structures obtainable from the midsagittal plane of the brain by two-dimensional sonography.

Methods: This was a prospective cross-sectional study of 434 healthy fetuses in low-risk singleton pregnancies between 18 and 35 gestational weeks. The following parameters were evaluated in the midsagittal cranial plane; cerebellar vermis anteroposterior diameter (APD), craniocaudal diameter (CCD), pons, midbrain and medulla oblongata APD and tectum length. The measurements were presented as growth charts according to gestational age.

Results: The mean ± SD, and 5%, 50%, 95% centile charts according to gestational age for vermis APD and CCD, pons, midbrain and medulla oblongata APD and tectum length were constructed. Pearson's correlation coefficients for vermis CCD and APD, pons, midbrain, medulla oblongata APD and tectum length by gestational week were 0.961, 0.929, 0.918, 0.761, 0.731 and 0.854, respectively (p < 0.0001).

Conclusion: The reference data provided in the present study would be helpful in the prenatal diagnosis of challenging fetal conditions with involvement of the brainstem and cerebellum.

Keywords: fetal; midbrain; pons; ultrasound; vermis.

© 2021 Wiley Periodicals LLC.