Screening for trisomy 21 with ultrasonographic determination of biparietal diameter/femur length ratio.
 Ultrasonographic determination of biparietal diameter/femur length ratios performed at 16 or 17 weeks' gestation in fetuses with trisomy 21 were not statistically different from those of 155 normal fetuses.
 It appears that this test could not be used for screening for trisomy 21.
