3D ultrasounds are best done at 24–32 weeks, and ideally between 26 and 30 weeks. Most 3d imaging centers advise customers to come in between 26 and 28 weeks to get the best images.
After 32 weeks, the fetus has descended into the pelvis and at that this time getting good 3D images of the fetus is still possible based on the expertise of the ultrasound technician. Clear images are possible to the end of the pregnancy depending on the position of the baby, placenta and amount of amniotic present around the face.

Within a couple of decades, 3D ultrasound will have totally supplanted the familiar 2D technology. That's the take of Stephen Smith, professor of biomedical engineering at Duke University (Durham, NC), who, with his colleague, Olaf von Ramm, pioneered the development of clinical 3D ultrasound scanners back in the 1980s. Since then, Smith and his research group have refined and adapted 3D ultrasound for a whole host of applications, and have market domination firmly in their sights.

Like regular ultrasounds, 3D and 4D ultrasounds use sound waves to create an image of your baby in your womb. What's different is that 3D ultrasounds create a three-dimensional image of your baby, while 4D ultrasounds create a live video effect, like a movie - you can watch your baby smile or yawn.

A 3D scan is a still three-dimensional image of your baby developing in the womb, whilst a 4D scan is a 3D image in full motion. This motion differentiates between a 3D and a 4D scan. Your scan will consist of both 3D and 4D, you will be able to purchase the 3D images on a USB and the 4D on a DVD for you to treasure.

A three-dimensional ultrasound, which uses high-frequency sound waves and special imaging software to provide incredibly clear images of your baby, can be done at any point in pregnancy in addition to or instead of a traditional, two-dimensional ultrasound. While 3D ultrasounds are becoming more common, there's really no medical benefit to having one for most women, so you may or may not be offered one as part of your routine prenatal care. If you'd like to have one anyway, check with your insurance to see if they'll cover it.The super-detailed images may be helpful if a potential problem is detected on a regular ultrasound. In these cases, being able to view the width, height, and depth of your baby and her internal organs can be helpful in making a diagnosis.

For foetal imaging, the big advantage has been in looking at facial and cranial abnormalities, and being able to measure the volumes of structures in the foetus. Also, 3D imaging allows you to measure things in directions that are not available in a normal 2D image. Cardiac 3D ultrasound is still growing, but it seems that the main advantages so far are being able to measure the volume of the left ventricle - otherwise known as the stroke volume or ejection fraction - and for guiding interventional devices, such as catheters, into the heart.