Fetal sex determination by ultrasound.

Real time ultrasonographic examination of the fetal perineal area after 30 weeks of gestation can reveal the external genitalia of the male fetus. The absence of this finding indicates a female fetus. This assessment is possible in up to two-thirds of cases, being limited only by the fetal presentation, position, and the estimated volume of amniotic fluid. Using this technique, fetal sexing was accomplished in 366 cases with an overall accuracy rate of 95.6% (correct in 99.5% of those diagnosed as males and in 91.5% of those diagnosed as females).