3D ultrasound is a medical ultrasound technique used mostly in obstetric ultrasound to provide three dimensional images of the fetus. 4D ultrasounds allow visualization of a 3D image in real time.

3D/4D ultrasounds are best done at 24- 28 weeks when there is adequate liquor volume.

Radiologists use 2D and Doppler ultrasounds regularly throughout pregnancy to examine the fetus, assess amniotic fluid and look for birth defects, among other things. The more-detailed 3D and 4D ultrasounds are performed during pregnancy to closely examine suspected fetal anomalies, such as cleft lip and spinal cord issues, or to monitor something specific.