3D/4D Obstetric Imaging

In standard 2D ultrasound imaging the picture seen on the screen is made up of thin slices of a particular area of your baby or pelvic organs. Only one thin slice is seen at a time, and although the sonographer can interpret this image it is often confusing for non-trained people.

3D ultrasound consists of a series of multiple 2D slices combined together to produce “life-like” pictures. No additional energy is required to generate a 3D image compared to a standard 2D image.

Current evidence does not demonstrate any adverse fetal effects from this technology, however in obstetrics, the benefits of 3D/4D obstetric imaging over standard 2D imaging are not yet well-defined.

The term “4D ultrasound” refers to four dimensional ultrasound, the fourth dimension being motion (time). Ultrasound using 4D technology essentially shows moving 3D images (like a video). This “live 3D” technology may be useful in assessing the fetal heart and fetal behaviour.

The basis of ultrasound diagnosis in obstetrics and gynaecology resides with classic 2D ultrasound imaging techniques.

In gynaecology imaging, 3D ultrasound is of particular use in the demonstration of abnormalities of uterine shape or internal pathology such as polyps of the endometrium (lining of the womb).

In obstetric imaging, 3D ultrasound can refine the 2D diagnosis of a fetal problem such as a facial cleft lip or a club foot. This can assist parents in understanding the nature of a problem if one is found. 

More often, 3D ultrasound is used to demonstrate the fetal face for parents with greater clarity than 2D facial pictures of the normal fetus. The addition of motion (4D) can be of assistance in viewing the fetal heart structures and fetal limb motion. The demonstration of fetal behaviours (eg. Yawning, smiling, eye opening) can be a profound bonding experience for parents.

Although we usually can obtain nice pictures of your baby with 3D or 4D technology, this is not always possible due to fetal position, placental location or other contributing factors.

The optimal timing for 3D/4D obstetric imaging is 22-26 weeks gestation when the fetus has some subcutaneous fat and the amniotic fluid volume is optimal. It is frequently very difficult to obtain satisfactory 3D images in the late third trimester.

The best time to schedule a 3D or 4D ultrasound is between 22 weeks and 26 weeks pregnant. The sonographers are able to achieve better results when the baby is smaller and the womb not completely full.

If you’re expecting twins or multiples, the best time for 3D/4D ultrasound is the same (between 22 and 27 weeks).

The most accurate method to determine the gender of a baby is the 2D ultrasound (black and white) which has 100% of accuracy in determining if it’s a boy or a girl. The 3D ultrasound may confirm the gender of the baby if is not clear from the 2D scan.

The most significant difference between 3D and 4D ultrasound is that with a 4D ultrasound you can see the “live streaming” video of the baby’s images. Both procedures allow you to see the baby in three-dimensional sequences using many 2D images taken from various angles and put together to form a three-dimensional image.

Before a 3D/4D ultrasound, there is some advice you can follow, like drinking many fluids in the days before the scan, eat something light before your appointment or have a glass of fruit juice. All these tips would help the baby moving during the exam.