Sonographic measurement of the fetal mandible: standards for normal pregnancy.

Measurements of the fetal mandible were made on 204 women with uncomplicated pregnancies and reliable gestational dates. The measurements were made in the sonographic plane, which included the fetal mandible and the hypopharynx. The antero-posterior and transverse jaw measurements increased with gestational age (p < 0.0001), and correlated well with both the biparietal diameter and femur length (p < 0.0001). Measurements were technically more difficult to obtain during the late third trimester. These standards for fetal jaw measurement may be useful in the sonographic identification of micrognathia.