Frontomaxillary facial angle in fetuses with trisomy 13 at 11 + 0 to 13 + 6 weeks.

OBJECTIVE To investigate the frontomaxillary facial (FMF) angle in fetuses with trisomy 13 at 11 + 0 to 13 + 6 weeks of gestation. METHODS A three-dimensional (3D) volume of the fetal head was obtained before karyotyping at 11 + 0 to 13 + 6 weeks of gestation in 23 fetuses with trisomy 13. The FMF angle, defined as the angle between the upper surface of the maxilla and the frontal bone in a midsagittal view of the fetal face, was measured and compared to the angle in 500 chromosomally normal fetuses. RESULTS In 10 of 12 (83.3%) fetuses with trisomy 13 and holoprosencephaly, the FMF angle was above the 95(th) centile of the normal range. In the 11 fetuses with no holoprosencephaly, the FMF angle was not significantly different from normal. There was no significant difference in the FMF angle between the trisomy 13 fetuses with and without facial cleft. CONCLUSIONS In fetuses with trisomy 13, the FMF angle at 11 + 0 to 13 + 6 weeks of gestation is increased only in cases with associated holoprosencephaly.