Study on normal reference value of fetal facial profile markers during the first trimester of pregnancy

Background: To establish a normal reference value for fetal facial profile markers during the first trimester of pregnancy. Methods: We collected the data of 800 pregnant women who were examined during early pregnancy. The range of values of inferior facial angle (IFA), frontal nasal-mental (FNM) angle, frontomaxillary facial (FMF) angle, mandibulomaxillary facial (MMF) angle, fetal profile line (FPL), and maxilla-nasion-mandible (MNM) angle in normal fetuses of 11–13⁺⁶ weeks was measured and correlated. For the 1,000 fetuses that were screened in the early pregnancy period (11–13⁺⁶ weeks), follow-up the normal fetus, observe and measure the above parameters to obtain the normal measurement range. These markers were measured through GE Voluson E8 ultrasound machines by two experienced sonographers. Results: A total of Images of 800 fetuses were included in the study. The results showed that the average value of fetal nasal bone was 11.9 mm at 11–13⁺⁶ weeks, which increased with the increase of crown-rump length (CRL); the average value of IFA angle was 64.91°, which has no obvious correlation with CRL; the average value of FNM angle was 143.79°, and the FNM angle decreased slightly with the increase of CRL. Both the FMF angle and the MMF angle decreased with the increase of CRL, and the ratio of FMF/MMF was fixed at 0.75; the average value of MNM angle was 9.55°, which had no obvious correlation with CRL; FP line value was “0” in 177 cases, The positive value of 623 cases did not change significantly with the growth of the fetus, and the gap of the mandible of the normal fetus was almost visible. Conclusions: This study established a range of normal reference values for facial and facial angles during early pregnancy, providing a reference for prenatal early detection, early diagnosis of fetal micrognathia, and other facial abnormalities.