Anatomy and growth of the fetal soft palate: a cadaveric study to improve its ultrasonographic observation.

Objective: To determine the anatomy of the soft and hard palate during fetal growth in order to improve its ultrasonographic prenatal visualization.
Design: Anatomic study in human formalin-fixed fetus.
Methods: The heads of 18 second and third trimester fetuses were studied in the median sagittal plan. Measurements of the soft palate, the velopharynx, the root of the tongue, and the oral floor were taken. The hard palate/soft palate angle and the anterior cranial base/soft palate angle were measured.
Results: The growth of the hard palate was linear, and the growth of the soft palate was polynomial (second order) during the period studied. The hard palate/soft palate angle was 150.33 degrees +/- 7.62 and 150.20 degrees +/- 6.67 in the second and third trimester, respectively. The anterior position of the soft palate in relation to the anterior cranial base was 48.8 degrees +/- 3.13 in the second trimester and 52.26 degrees +/- 3.31 in the third trimester. Its posterior position was 89.66 degrees +/- 5.51 in the second trimester and 92.97 degrees +/- 4.01 in the third trimester. Throughout the fetal period, the soft palate moved downward relative to the clivus and cervical spine.
Conclusions: Despite the nonlinear growth and downward displacement of the soft palate during fetal life, its position remains stable. These results may be useful to explore the fetal soft palate using 2D and 3D ultrasonography and to improve the prenatal diagnosis of isolated cleft palate.