(HealthDay)—Three-dimensional (3D) virtual reality ultrasound is not accurate in first-trimester fetal sex determination, according to a study published online Oct. 19 in the Journal of Clinical Ultrasound.

Hein Bogers, M.D., from Erasmus Medical Center in the Netherlands, and colleagues obtained 3D volumes in 112 pregnancies between nine and 13 gestational weeks. They were projected offline as a hologram, and the genital tubercle angle was measured. The 3D ultrasound aspect of the genitalia was examined for male or female appearance.

The researchers found that there was a significant difference in genital tubercle angles between male and female fetuses, but it was not a reliable predictor of gender. Based on first-trimester genital appearance, correct sex prediction was 56 percent at best.

"Our results indicate that accurate determination of the fetal sex in the first trimester of pregnancy is not possible, even using an advanced 3D ," the authors write. "If fetal sex has to be determined, other techniques like DNA sequencing should be used."