To evaluate the fetal profile (FP) line with two-dimensional and three dimensional ultrasound, to explore the changes of fetal facial profile with gestational age,and to analyze the manifestation of FP line for abnormal chromosomal fetuses.

FP line, which was defined as the line that passes through the anterior border of mandible and the nasion, was test on the facial mid-sagittal plane. Firstly, from April 2013 to January 2014, FP line was analyzed in 439 normal fetuses of Peking Union Medical College Hospital at 11-38 weeks of gestation. According to the relationship between FP line and fetal frontal bone,it was divided into three types: the FP line passed anteriorly, across or posteriorly to the frontal bone, respectively. When the FP line passed posteriorly to the frontal bone, the distance (F distance) between the FP line with the frontal bone was measured. Secondly, 26 pathological fetuses (21 trisomy 21 fetuses with 13-33 weeks′ gestation and 5 trisomy 18 fetuses with 21-31 weeks′ gestation) were analyzed respectively.

No cases with a FP line passed anteriorly to the frontal bone were found in all of normal fetuses. Most commonly seen was that FP line passed across to the frontal bone (92.26%). The FP line passed posteriorly to the frontal bone in up to 7.74%, and the mean F distance was 0.24 cm (range, 0.10-0.51 cm). In 21 fetuses of trisomy 21, 14 cases showed the FP line passed across to frontal bone, and 4 cases showed the FP line passed posteriorly frontal bone with the F distance from 0.23 cm to 0.55 cm. Three cases with sloping forehead with FP line passed anteriroly to frontal bone. As to 5 cases of trisomy 18, 2 cases showed FP line passed across to frontal bone, and 3 cases with micrognathia had FP line passed anteriroly to frontal bone.

No cases with a FP line passed anteriorly to the frontal bone were found in normal fetuses. The FP line, as a reference line for forehead and mandible abnormality, may be a useful tool to detect second trimester profile abnormalities such as sloping forehead and retrognathia.