The sagittal sign. An early second trimester sonographic indicator of fetal gender.

The sagittal sign for sonographic prediction of fetal gender in the early second trimester is described and its sensitivity and accuracy evaluated. One hundred eighty-four ultrasound examinations with gestational ages between 10 weeks and 20.5 weeks were performed in 165 patients over a three month period. Of the 165 patients included in this prospective study, the gender of the fetus in 105 patients was known as a result of amniocentesis or chorionic villus sampling. These 105 patients with known results were used to compare gender prediction based on conventional views with prediction based on the sagittal sign. The results of this study reveal the superiority of the sagittal view for predicting gender in the gestational age group of 14 weeks to 20.5 weeks.