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Your doctor may request a Third Trimester ultrasound for many reasons

  1. To check the Placenta: Review of the position of the placenta if it was low lying in 18-20 week scan, or if you have unexplained vaginal bleeding.
  2. To assess baby’s size: If your doctor is concern that your baby is too small, not growing well or too large. Some conditions may affect the growth such as diabetes or high blood pressure.
  3. The well being of your baby can be assessed if our are experiencing vaginal bleeding, reduced fetal movements or premature contractions.
  4. To assess baby position: If your doctors are unsure of the fetal lie towards the end of the pregnancy, a scan can determined if it is lying in the Breech, Transverse or Cephalic position.
  5. Review of the baby’s anatomy: Your doctor may wish to review a change, or abnormality in your baby which is noted at 18-20 weeks scan.
  6. You have a Twin /Multiple pregnancies: Multiple pregnancies are at higher risk of growth problems during pregnancy.

What measurements will be taken?

Biparietal Diameter(BPD)  and Head Circumference (HC)

Abdominal Circumference

Femur and Humeral length

These measurements are combined in a special formula to estimate the weight of your baby.
The amount of the amniotic fluid around your baby is calculated by measuring the maximal vertical distance of fluid in each quadrant known as AFI.  If the AFI is increased (polyhydramnios) can be associated with diabetes. If  the AFI  is decreased (oligohydramnios)  can be associated with small babies.

Doppler Blood Flow

The blood flow in the umbilical artery and the middle cerebral artery in the baby’s brain will be measured. Sometimes Ductus Venosus (in the liver) will also be measured. They help to assess the function of the placenta and the health and well being of your baby.  Babies that are growth restricted may show progressive changes in the blood flow of these vessels. Monitoring of these changes can help your doctor to decide when the needs to be delivered.

The baby’s heart rate and rhythm.

The baby’s position.

The ultrasound will tell us what position the baby is lying in

  • Head down (Cephalic Position)
  • Bottom down, head up (breech position)
  • Sideways (transverse position)

Placental position

The doctors want to know how close the lower edge of the placenta from the cervix is.  If  the concern that your placenta is close than a trans-vaginal scan will be required to get a closer  look at the distance and if there are any vessels in the way.

The Anatomy of the Baby

As the baby grows, the anatomy of the baby is limited to what we can see.  Structures that are routinely reviewed in third trimester are kidneys, bladder etc. 

Length  of Cervix

Is checked if you have had a premature labour or are having contractions in early third trimester

Make an Appointment

If you have a referral - please give
us a call on (07) 5539 2555.

We accept all referrals. 

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