Forehead and facial heights in Down syndrome and normal fetuses in the midtrimester of pregnancy

Abstract

Objectives: To compare forehead height (FH), facial heights (FaHs) and the ratios of biparietal diameter (BPD) and femur length (FL) to these heights in midtrimester normal and Down syndrome (DS) fetuses. Methods: 150 normal and 26 DS fetuses were scanned at 15-25 weeks of gestation. At the mid-sagittal image of the fetal profile, FH, FaH, upper facial height (UFaH) and lower facial height (LFaH) were measured in millimeters with "two line distance" tool. The results were expressed as multiples of the gestation-specific normal median (MoMs) using the regression of the equation derived from normal fetuses. The ratios of BPD/UFaH, BPD/LFaH, BPD/FaH, BPD/FH, FL/UFaH, FL/LFaH, FL/FaH, FL/FH were also assessed. Results: In normal fetuses, FH and FaHs increased linearly with gestational age (GA). UFaH increased linearly from 5.2 mm at 15 weeks to 15.7 mm at 25 weeks. LFaH increased from 9.3 mm at 15 weeks to 32 mm at 25.2 weeks. FaH increased from 16 mm at 15 weeks to 39 mm at 25 weeks. FH increased from 17.7 mm at 15 weeks to 42.8 mm at 25 weeks. Only UFaH was found to be significantly smaller in DS fetuses (with a mean of 0.91 MoM, 95% CI, 0.7-1.1, p = 0.003), than in normal fetuses (1 MoM, 95% CI, 0.6-1.3). Concomitantly, none of the ratios changed with gestation and all were found to be statistically higher in DS fetuses (p < 0.05). Conclusions: UFaH, is smaller in DS fetuses compared with normal fetuses in the midtrimester of pregnancy. The ratios of BPD and FL to all heights are higher in fetuses with DS than in normal fetuses.