The frontal space measurement in euploid and aneuploid pregnancies at 11-13 weeks' gestation.

OBJECTIVE

The aim of this study is to evaluate whether the measurement of the frontal space (FS) improves first trimester combined aneuploidy screening.

METHODS

We have presented a retrospective study including 2D images of the nuchal translucency measurement of 300 euploid and 133 trisomic fetuses that were seen at the prenatal department at the University of Tuebingen, Germany. For the FS measurement, a mandibulo-maxillary line (MML) was created by connecting the anterior edge of the mental protuberance and anterior edge of the maxilla. The MML was then extended upwards. A measurement was taken perpendicular from the MML to the skin line over the point of largest excursion of the fetal forehead. After transformation into z-scores based on the crown rump length, the FS distribution in fetuses with trisomy 21, 18, and 13 was compared with the euploid group by using a student's t-test.

RESULTS

The mean FS in euploid fetuses was 1.25 mm. In fetuses with trisomy 21, 18, and 13, the mean FS measurements were 2.96, 3.22, and 2.03 mm. In euploid and trisomy 21, 18, and 13 pregnancies, FS measurements were above the 95th centile in 5.3%, 41.1%, 34.3%, and 12.5% of the cases. The mean z-scores were significantly higher in trisomy 21 and 18.

CONCLUSION

First trimester FS measurement may improve first trimester combined screening.