A baby's gender can typically be seen on ultrasound starting around 16 weeks of gestation when the baby's anatomy is developed enough to give an accurate confirmation. Earlier attempts to determine gender using ultrasound, such as the "nub theory," can be done around 11 to 13 weeks but are less common and less reliable. By 16 weeks and up to about 32 weeks, ultrasound can more reliably show gender depending on the baby's position and equipment quality. Before 16 weeks, gender predictions with ultrasound tend to be much less reliable.
In some studies, ultrasound gender identification at 11-12 weeks has shown around 91% accuracy, but it's generally more accurate after 16 weeks. Gender determination before this time might be possible but not guaranteed, and later scans, especially the anatomy scan around 20 weeks, are more definitive.
Thus, for practical and typical ultrasound use, gender can usually be seen reliably from about 16 weeks of pregnancy onwards.
