Mandibular dimensions and growth in 11- to 26-week-old Danish fetuses studied by 3D ultrasound

To present normative data on prenatal mandibular morphology and growth.

Fifty-four normal fetuses (Danish Caucasian) were included in the study (gestational age: 11-26 weeks). Fetuses were scanned using a GE Voluson 730 Expert 3D scanner. Scans were visualized and analyzed using GE 4DVIEW software. Mandibular dimensions [base length (B), ramus height (H), and total length (L)] and the mandibular angle (phi) were measured, and the mandibular index was calculated. Method error was estimated by duplicate measurements. Growth was calculated by regressing measured variables on age.

Mandibular measurements were found to be reliable [precision: 0.5-1.2 mm (1SD)]. Mean mandibular variable values at week 11: B = 5.2 +/- 2.5 mm; H = 2.7 +/- 1.3 mm; L = 7.7 +/- 3.2 mm; phi = 149 +/- 6.0 degrees; and at week 26: B = 22.6 +/- 2.5 mm; H = 12.3 +/- 1.3 mm; L = 33.1 +/- 3.2 mm; phi = 135 +/- 6.0 degrees. A linear model described growth (B(g)/H(g)/L(g)/phi(g)) giving B(g) = 1.2; H(g) = 0.64; L = 1.7 mm/week; phi(g) = - 0.9 degrees/week.

Normative 3D data values for the human mandible in 11- to 26-week-old fetuses were presented. All measured mandibular parameters could be described using a linear increasing model from 11 to 26 weeks. All linear dimensions increased in size, while the mandibular angle decreased steadily during the observation period.