Frontomaxillary facial angle measurement in trisomy 21 and euploid fetuses: two- and three-dimensional assessment during routine first trimester screening.

OBJECTIVE: To assess 2D and 3D frontomaxillary facial angle (FMFA) measurements in euploid and trisomy 21 fetuses.

MATERIALS AND METHODS: Over a 2-year period, women with singleton pregnancies attending a private prenatal screening and diagnosis practice in Sydney, Australia, were invited to participate in this study where 2D images and 3D volumes of the fetal face were collected during routine first trimester screening. In pregnancies where trisomy 21 was confirmed, FMFA measurements were performed in 2D and 3D and compared with those from a euploid cohort.

RESULTS: Overall, 250 women carrying euploid and 22 women carrying trisomy 21 fetuses participated. Trisomy 21 fetuses had significantly larger FMFA measurements than euploid fetuses in both 2D and 3D assessments. 95% of 3D and 100% of 2D FMFA measurements for the trisomy 21 fetuses were above the mean FMFA measurement of the euploid fetuses. There was no relationship between increasing crown-rump length and FMFA measurement.

CONCLUSION: 2D and 3D FMFA measurements in trisomy 21 fetuses are statistically greater (p < 0.001) than those in euploid fetuses. This supports FMFA as a possible additional marker for trisomy 21 for first trimester screening.