Objective: To establish the normal range of the frontomaxillary facial (FMF) angle of the chineses fetuses at 11 + 0 to 13+6 weeks gestation.
Methods: A prospective observational study was performed on 600 cases of pregnancies at the first trimester ultrasound screening between 11 and 13+6 weeks (crown-rump length between 45mm to 84mm).Nuchal translucency thickness(NT), CRL,FMF angle were measured in first trimester screening and maternal serum free β-hCG and AFP were collected in the second trimester. Transabdominal ultrasound examination was performed on a GE Voluson 730. The FMF angle measured in the midsagittal plane of the fetal profile. High risk cases underwent amniocentesis to demonstrate the fetus chromosomally normal. In a subgroup of 350 cases the FMF angle was measured using 3D ultrasound after 2D ultrasound.
Results: The mean FMF angle decreased with CRL. There was no significant correlation between the FMF angle and fetal NT or maternal serum biochemistry.In those cases with paired measurements there was no statistical difference between 2D and 3D ultrasound measurement.
Conclusions: This study demonstrates that at 11–13+6 weeks, the fetal FMF angle reduces with CRL and gestational age but is not related to fetal NT or maternal serum biochemistry.