Third Trimester Ultrasound


Not all pregnant women need a third trimester ultrasound. Some of the reasons why a third trimester ultrasound may be requested are listed below:

  • If clinically the fetus feels larger or smaller than expected for the gestation

  • If the mother has a medical condition that may influence fetal growth and well-being

  • If the placenta was low-lying on the midtrimester ultrasound.

  • If the clinician is uncertain about the position of the fetal head

  • If there is pain of bleeding

  • If the fetus is not moving well

  • If a fetal abnormality was noted on an earlier ultrasound

More and more obstetricians refer women for two third trimester ultrasounds, mostly at 28 weeks and 36 weeks, because there is increasing evidence that this allows better detection of growth problems and ensures better outcomes for babies.

On a third trimester ultrasound we always check:

  • Fetal anatomy, although late in pregnancy the views of certain parts of the fetus may be difficult.

  • Fetal position.

  • Placental position

  • Fetal size. An estimated fetal weight is calculated from measuring the fetal head, abdomen and femur. There can be a 15% error on the weight estimate.

  • Fetal well-being. We check fetal movement, tone, breathing and liquor volume and give the fetus a biophysical score which is indicative of its well-being. The maximum score on ultrasound is 8/8.

  • The blood flow in the umbilical cord, which gives an idea of placental function

Photographs and Videos

The ultrasound examination will be recorded on USB free of charge. We will also send a picture of your baby to your phone by mms.


We welcome children at our practice. There are toys provided in the waiting area. Small children however are rarely able to relate to the images on the screen and may become restless, decreasing your and your partner's enjoyment of the ultrasound experience.

3D and 4D Ultrasound

Although 3D and 4D ultrasound can create some absolutely fantastic images of the unborn baby, it is very much dependent on the gestation and the position of the baby. We usually check the fetus in 2D first, to make sure that all is well. At the end of the examination, we do a 3D or 4D ultrasound. It is best to attend a 3D or 4D ultrasound with an open mind, realising that not everyone gets a 'as we've seen it on TV' image. We get beautiful images of the face if the baby is facing up and there is sufficient fluid around baby's face, but that is unfortunately not so every time. We will always try to get the best images in every situation but keeping the limitations of 3 and 4D ultrasound in mind avoids disappointment.