The 20 week morphology ultrasound may be the final scan in your pregnancy. In some cases, follow-up ultrasound imaging may be required.

The most common reasons for a follow-up scan after the 20 week morphology scan include:

  • Growth assessment (if you appear to be having a large or small baby).
  • Gestational diabetes.
  • High blood pressure.
  • Placental position.
  • Monitor a multiple pregnancy (twins/triplets).
  • Check the baby’s position.
  • Assessment of the blood flow to the baby (Doppler scan).
  • Bleeding or fluid loss.

The 20-week morphology scan will assess the general wellbeing of the baby and take measurements to look at the baby’s growth, placental position, blood flow to the baby, and the amount of fluid surrounding the baby.

In most cases, the ultrasound will be performed transabdominally, but there are some situations where an internal or transvaginal ultrasound may be necessary. Transvaginal ultrasound involves placing a thin transducer (slightly thicker than a tampon) into the vagina. The transvaginal ultrasound can offer extra detail to the examination as the ultrasound probe comes into close proximity to the uterus.  A transvaginal scan is optional; it is your decision whether to proceed.

Transabdominal and transvaginal ultrasound are safe at all stages of pregnancy.

Before your Scan

If possible, please wear comfortable, loose-fitting clothing for easy access to your abdomen. Two-piece clothing is ideal (separate upper/lower garments).

Transabdominal:   Drink 500mL of water one hour before your appointment and do not empty your bladder. Your bladder does not need to be so full that it causes you pain or distress; if this is the case, please tell reception staff on arrival, and they will talk to you about your options. If during the examination, your bladder is causing you discomfort, please tell the sonographer.

Transvaginal: If this imaging is required, it is done on an empty bladder.

Preparation details for your examination will be confirmed when you make your appointment.


Approximately 30 minutes.

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