Nomogram for the Measurements of the Fetal Maxillary Bone During the First Trimester Screening for Down Syndrome

Objective: To define a nomogram of fetal maxillary bone length for a Turkish population between 11 and 13(+6)weeks' gestation. Materials and Methods: This was a prospective observational and cross-sectional study over 12 months examining Turkish women with a singleton pregnancy who attended the first-trimester screening program for Down syndrome. Consecutive routine biometric measurements and fetal organ scans were obtained from patients. Special attention was paid to the profile view of die fetal face, and die maxillary bone was identified and measured. Results: Four hundred and three fetuses between 11 and 13(+6) weeks' gestation were scanned. The maxillary bone is seen as a rodlike structure; it; is a parr of the facial skeleton that allows the opening and closing of the pharynx. A linear growth function was observed across gestational age, and good con-elation was found to exist between crown-rump length (CRL) and the maxillary bone (r=0.662; p<0.0001; y=2.328+0.068xCRL). Significant correlation was also found between the maxillary bone and biparietal diameter (BPD) (r=0.693; p<0.0001; y=1.703+0.226xBPD), head circumference (HC) (r=0.704; p<0.0001; y=1.380+0.066xHC), femoral bone length (FL) (r=0.678; p<0.0001; y=4.303+0.287xFL), and abdominal circumference (AC) (r=0.705; p<0.0001; y=1.552+0.081xAC). Discussion: Normative data for sonographic measurements of the fetal maxillary bone between 11 and 1.(3+6) weeks' gestation are provided. These data potentially allow the prenatal diagnosis of abnormal maxillary bone length.