Ultrasounds are seen as a routine diagnostic tool by most medical professionals that provide care for pregnant women. But 2D ultrasounds are still the norm. In 2D ultrasound, the sounds waves are sent and then reflected straight back, while 3D ultrasound involves sending sound waves at various angles, and the information returned to the machine being processed by a computer. Some say that the risks of 3D ultrasound are unclear, and that anyone going for a 3D or 4D ultrasound should understand that risks may exist. Ultrasound is known to produce heat, and the duration of 4D scans should certainly be limited because of that reason.
Although 4D ultrasounds exist solely for private, non-medical reasons, this does not mean that there are no benefits at all. The ultrasound technician carrying out such scans could possibly notice medical problems during the ultrasound. If there are obvious anomalies, they may just be diagnosed during a "keepsake ultrasound", as these 4D ultrasounds are also known as. You may also find out your baby's gender through ultrasound, which isn't really a medical benefit, but still important to many. Additionally, the location of the placenta, and any placental conditions such as placenta accreta or placenta previa, may become obvious during a 4D ultrasound.